853 lines
32 KiB
XML
853 lines
32 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!--
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The FreeBSD Documentation Project
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$FreeBSD$
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-->
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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:id="filesystems">
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<info>
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<title>File Systems Support</title>
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<authorgroup>
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<author><personname><firstname>Tom</firstname><surname>Rhodes</surname></personname><contrib>Written
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by </contrib></author>
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</authorgroup>
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</info>
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<sect1 xml:id="filesystems-synopsis">
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<title>Synopsis</title>
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<indexterm><primary>File Systems</primary></indexterm>
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<indexterm>
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<primary>File Systems Support</primary>
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<see>File Systems</see>
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</indexterm>
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<para>File systems are an integral part of any operating system.
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They allow users to upload and store files, provide access
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to data, and make hard drives useful. Different operating
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systems differ in their native file system. Traditionally, the
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native &os; file system has been the Unix File System
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<acronym>UFS</acronym> which has been modernized as
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<acronym>UFS2</acronym>. Since &os; 7.0, the Z File
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System <acronym>ZFS</acronym> is also available as a native file
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system.</para>
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<para>In addition to its native file systems, &os; supports a
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multitude of other file systems so that data from other
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operating systems can be accessed locally, such as data stored
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on locally attached <acronym>USB</acronym> storage devices,
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flash drives, and hard disks. This includes support for the
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&linux; Extended File System (<acronym>EXT</acronym>) and the
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Reiser file system.</para>
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<para>There are different levels of &os; support for the various
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file systems. Some require a kernel module to be loaded and
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others may require a toolset to be installed. Some non-native
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file system support is full read-write while others are
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read-only.</para>
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<para>After reading this chapter, you will know:</para>
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<itemizedlist>
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<listitem>
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<para>The difference between native and supported file
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systems.</para>
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</listitem>
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<listitem>
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<para>Which file systems are supported by &os;.</para>
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</listitem>
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<listitem>
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<para>How to enable, configure, access, and make use of
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non-native file systems.</para>
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</listitem>
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</itemizedlist>
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<para>Before reading this chapter, you should:</para>
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<itemizedlist>
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<listitem>
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<para>Understand &unix; and <link
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linkend="basics">&os; basics</link>.</para>
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</listitem>
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<listitem>
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<para>Be familiar with the basics of <link
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linkend="kernelconfig">kernel configuration and
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compilation</link>.</para>
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</listitem>
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<listitem>
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<para>Feel comfortable <link linkend="ports">installing
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software</link> in &os;.</para>
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</listitem>
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<listitem>
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<para>Have some familiarity with <link
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linkend="disks">disks</link>, storage, and device names in
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&os;.</para>
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</listitem>
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</itemizedlist>
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</sect1>
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<sect1 xml:id="filesystems-zfs">
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<title>The Z File System (ZFS)</title>
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<para>The Z file system, originally developed by &sun;,
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is designed to use a pooled storage method in that space is only
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used as it is needed for data storage. It is also designed for
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maximum data integrity, supporting data snapshots, multiple
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copies, and data checksums. It uses a software data replication
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model, known as <acronym>RAID</acronym>-Z.
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<acronym>RAID</acronym>-Z provides redundancy similar to
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hardware <acronym>RAID</acronym>, but is designed to prevent
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data write corruption and to overcome some of the limitations
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of hardware <acronym>RAID</acronym>.</para>
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<sect2>
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<title>ZFS Tuning</title>
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<para>Some of the features provided by <acronym>ZFS</acronym>
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are RAM-intensive, so some tuning may be required to provide
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maximum efficiency on systems with limited RAM.</para>
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<sect3>
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<title>Memory</title>
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<para>At a bare minimum, the total system memory should be at
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least one gigabyte. The amount of recommended RAM depends
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upon the size of the pool and the ZFS features which are
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used. A general rule of thumb is 1GB of RAM for every 1TB
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of storage. If the deduplication feature is used, a general
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rule of thumb is 5GB of RAM per TB of storage to be
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deduplicated. While some users successfully use ZFS with
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less RAM, it is possible that when the system is under heavy
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load, it may panic due to memory exhaustion. Further tuning
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may be required for systems with less than the recommended
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RAM requirements.</para>
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</sect3>
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<sect3>
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<title>Kernel Configuration</title>
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<para>Due to the RAM limitations of the &i386; platform, users
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using ZFS on the &i386; architecture should add the
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following option to a custom kernel configuration file,
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rebuild the kernel, and reboot:</para>
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<programlisting>options KVA_PAGES=512</programlisting>
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<para>This option expands the kernel address space, allowing
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the <varname>vm.kvm_size</varname> tunable to be pushed
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beyond the currently imposed limit of 1 GB, or the
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limit of 2 GB for <acronym>PAE</acronym>. To find the
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most suitable value for this option, divide the desired
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address space in megabytes by four (4). In this example, it
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is <literal>512</literal> for 2 GB.</para>
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</sect3>
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<sect3>
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<title>Loader Tunables</title>
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<para>The <filename>kmem</filename> address space can
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be increased on all &os; architectures. On a test system
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with one gigabyte of physical memory, success was achieved
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with the following options added to
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<filename>/boot/loader.conf</filename>, and the system
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restarted:</para>
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<programlisting>vm.kmem_size="330M"
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vm.kmem_size_max="330M"
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vfs.zfs.arc_max="40M"
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vfs.zfs.vdev.cache.size="5M"</programlisting>
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<para>For a more detailed list of recommendations for
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ZFS-related tuning, see <uri
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xlink:href="http://wiki.freebsd.org/ZFSTuningGuide">http://wiki.freebsd.org/ZFSTuningGuide</uri>.</para>
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</sect3>
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</sect2>
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<sect2>
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<title>Using <acronym>ZFS</acronym></title>
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<para>There is a start up mechanism that allows &os; to mount
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<acronym>ZFS</acronym> pools during system initialization. To
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set it, issue the following commands:</para>
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<screen>&prompt.root; <userinput>echo 'zfs_enable="YES"' >> /etc/rc.conf</userinput>
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&prompt.root; <userinput>service zfs start</userinput></screen>
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<para>The examples in this section assume three
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<acronym>SCSI</acronym> disks with the device names
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<filename><replaceable>da0</replaceable></filename>,
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<filename><replaceable>da1</replaceable></filename>,
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and <filename><replaceable>da2</replaceable></filename>.
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Users of <acronym>IDE</acronym> hardware should instead use
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<filename><replaceable>ad</replaceable></filename>
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device names.</para>
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<sect3>
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<title>Single Disk Pool</title>
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<para>To create a simple, non-redundant <acronym>ZFS</acronym>
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pool using a single disk device, use
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<command>zpool</command>:</para>
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<screen>&prompt.root; <userinput>zpool create example /dev/da0</userinput></screen>
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<para>To view the new pool, review the output of
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<command>df</command>:</para>
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<screen>&prompt.root; <userinput>df</userinput>
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/ad0s1a 2026030 235230 1628718 13% /
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devfs 1 1 0 100% /dev
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/dev/ad0s1d 54098308 1032846 48737598 2% /usr
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example 17547136 0 17547136 0% /example</screen>
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<para>This output shows that the <literal>example</literal>
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pool has been created and <emphasis>mounted</emphasis>. It
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is now accessible as a file system. Files may be created
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on it and users can browse it, as seen in the following
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example:</para>
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<screen>&prompt.root; <userinput>cd /example</userinput>
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&prompt.root; <userinput>ls</userinput>
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&prompt.root; <userinput>touch testfile</userinput>
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&prompt.root; <userinput>ls -al</userinput>
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total 4
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drwxr-xr-x 2 root wheel 3 Aug 29 23:15 .
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drwxr-xr-x 21 root wheel 512 Aug 29 23:12 ..
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-rw-r--r-- 1 root wheel 0 Aug 29 23:15 testfile</screen>
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<para>However, this pool is not taking advantage of any
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<acronym>ZFS</acronym> features. To create a dataset on
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this pool with compression enabled:</para>
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<screen>&prompt.root; <userinput>zfs create example/compressed</userinput>
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&prompt.root; <userinput>zfs set compression=gzip example/compressed</userinput></screen>
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<para>The <literal>example/compressed</literal> dataset is now
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a <acronym>ZFS</acronym> compressed file system. Try
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copying some large files to
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<filename>/example/compressed</filename>.</para>
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<para>Compression can be disabled with:</para>
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<screen>&prompt.root; <userinput>zfs set compression=off example/compressed</userinput></screen>
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<para>To unmount a file system, issue the following command
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and then verify by using <command>df</command>:</para>
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<screen>&prompt.root; <userinput>zfs umount example/compressed</userinput>
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&prompt.root; <userinput>df</userinput>
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/ad0s1a 2026030 235232 1628716 13% /
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devfs 1 1 0 100% /dev
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/dev/ad0s1d 54098308 1032864 48737580 2% /usr
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example 17547008 0 17547008 0% /example</screen>
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<para>To re-mount the file system to make it accessible
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again, and verify with <command>df</command>:</para>
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<screen>&prompt.root; <userinput>zfs mount example/compressed</userinput>
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&prompt.root; <userinput>df</userinput>
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/ad0s1a 2026030 235234 1628714 13% /
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devfs 1 1 0 100% /dev
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/dev/ad0s1d 54098308 1032864 48737580 2% /usr
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example 17547008 0 17547008 0% /example
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example/compressed 17547008 0 17547008 0% /example/compressed</screen>
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<para>The pool and file system may also be observed by viewing
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the output from <command>mount</command>:</para>
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<screen>&prompt.root; <userinput>mount</userinput>
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/dev/ad0s1a on / (ufs, local)
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devfs on /dev (devfs, local)
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/dev/ad0s1d on /usr (ufs, local, soft-updates)
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example on /example (zfs, local)
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example/data on /example/data (zfs, local)
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example/compressed on /example/compressed (zfs, local)</screen>
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<para><acronym>ZFS</acronym> datasets, after creation, may be
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used like any file systems. However, many other features
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are available which can be set on a per-dataset basis. In
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the following example, a new file system,
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<literal>data</literal> is created. Important files will be
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stored here, the file system is set to keep two copies of
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each data block:</para>
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<screen>&prompt.root; <userinput>zfs create example/data</userinput>
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&prompt.root; <userinput>zfs set copies=2 example/data</userinput></screen>
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<para>It is now possible to see the data and space utilization
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by issuing <command>df</command>:</para>
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<screen>&prompt.root; <userinput>df</userinput>
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/ad0s1a 2026030 235234 1628714 13% /
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devfs 1 1 0 100% /dev
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/dev/ad0s1d 54098308 1032864 48737580 2% /usr
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example 17547008 0 17547008 0% /example
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example/compressed 17547008 0 17547008 0% /example/compressed
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example/data 17547008 0 17547008 0% /example/data</screen>
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<para>Notice that each file system on the pool has the same
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amount of available space. This is the reason for using
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<command>df</command> in these examples, to show that the
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file systems use only the amount of space they need and all
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draw from the same pool. The <acronym>ZFS</acronym> file
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system does away with concepts such as volumes and
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partitions, and allows for several file systems to occupy
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the same pool.</para>
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<para>To destroy the file systems and then destroy the pool as
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they are no longer needed:</para>
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<screen>&prompt.root; <userinput>zfs destroy example/compressed</userinput>
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&prompt.root; <userinput>zfs destroy example/data</userinput>
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&prompt.root; <userinput>zpool destroy example</userinput></screen>
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</sect3>
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<sect3>
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<title><acronym>ZFS</acronym> RAID-Z</title>
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<para>There is no way to prevent a disk from failing. One
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method of avoiding data loss due to a failed hard disk is to
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implement <acronym>RAID</acronym>. <acronym>ZFS</acronym>
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supports this feature in its pool design.</para>
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<para>To create a <acronym>RAID</acronym>-Z pool, issue the
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following command and specify the disks to add to the
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pool:</para>
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<screen>&prompt.root; <userinput>zpool create storage raidz da0 da1 da2</userinput></screen>
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<note>
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<para>&sun; recommends that the amount of devices used in
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a <acronym>RAID</acronym>-Z configuration is between
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three and nine. For environments requiring a single pool
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consisting of 10 disks or more, consider breaking it up
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into smaller <acronym>RAID</acronym>-Z groups. If only
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two disks are available and redundancy is a requirement,
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consider using a <acronym>ZFS</acronym> mirror. Refer to
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&man.zpool.8; for more details.</para>
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</note>
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<para>This command creates the <literal>storage</literal>
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zpool. This may be verified using &man.mount.8; and
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&man.df.1;. This command makes a new file system in the
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pool called <literal>home</literal>:</para>
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<screen>&prompt.root; <userinput>zfs create storage/home</userinput></screen>
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<para>It is now possible to enable compression and keep extra
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copies of directories and files using the following
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commands:</para>
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<screen>&prompt.root; <userinput>zfs set copies=2 storage/home</userinput>
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&prompt.root; <userinput>zfs set compression=gzip storage/home</userinput></screen>
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<para>To make this the new home directory for users, copy the
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user data to this directory, and create the appropriate
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symbolic links:</para>
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<screen>&prompt.root; <userinput>cp -rp /home/* /storage/home</userinput>
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&prompt.root; <userinput>rm -rf /home /usr/home</userinput>
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&prompt.root; <userinput>ln -s /storage/home /home</userinput>
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&prompt.root; <userinput>ln -s /storage/home /usr/home</userinput></screen>
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<para>Users should now have their data stored on the freshly
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created <filename>/storage/home</filename>. Test by
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adding a new user and logging in as that user.</para>
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<para>Try creating a snapshot which may be rolled back
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later:</para>
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<screen>&prompt.root; <userinput>zfs snapshot storage/home@08-30-08</userinput></screen>
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<para>Note that the snapshot option will only capture a real
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file system, not a home directory or a file. The
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<literal>@</literal> character is a delimiter used between
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the file system name or the volume name. When a user's
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home directory gets trashed, restore it with:</para>
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<screen>&prompt.root; <userinput>zfs rollback storage/home@08-30-08</userinput></screen>
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<para>To get a list of all available snapshots, run
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<command>ls</command> in the file system's
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<filename>.zfs/snapshot</filename> directory. For example,
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to see the previously taken snapshot:</para>
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<screen>&prompt.root; <userinput>ls /storage/home/.zfs/snapshot</userinput></screen>
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<para>It is possible to write a script to perform regular
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snapshots on user data. However, over time, snapshots
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may consume a great deal of disk space. The previous
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snapshot may be removed using the following command:</para>
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<screen>&prompt.root; <userinput>zfs destroy storage/home@08-30-08</userinput></screen>
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<para>After testing, <filename>/storage/home</filename> can be
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made the real <filename>/home</filename> using this
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command:</para>
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<screen>&prompt.root; <userinput>zfs set mountpoint=/home storage/home</userinput></screen>
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<para>Run <command>df</command> and
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<command>mount</command> to confirm that the system now
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treats the file system as the real
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<filename>/home</filename>:</para>
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<screen>&prompt.root; <userinput>mount</userinput>
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/dev/ad0s1a on / (ufs, local)
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devfs on /dev (devfs, local)
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/dev/ad0s1d on /usr (ufs, local, soft-updates)
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storage on /storage (zfs, local)
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storage/home on /home (zfs, local)
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&prompt.root; <userinput>df</userinput>
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/ad0s1a 2026030 235240 1628708 13% /
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devfs 1 1 0 100% /dev
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/dev/ad0s1d 54098308 1032826 48737618 2% /usr
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storage 26320512 0 26320512 0% /storage
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storage/home 26320512 0 26320512 0% /home</screen>
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<para>This completes the <acronym>RAID</acronym>-Z
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configuration. To get status updates about the file systems
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created during the nightly &man.periodic.8; runs, issue the
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following command:</para>
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<screen>&prompt.root; <userinput>echo 'daily_status_zfs_enable="YES"' >> /etc/periodic.conf</userinput></screen>
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</sect3>
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<sect3>
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<title>Recovering <acronym>RAID</acronym>-Z</title>
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<para>Every software <acronym>RAID</acronym> has a method of
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monitoring its <literal>state</literal>. The status of
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<acronym>RAID</acronym>-Z devices may be viewed with the
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following command:</para>
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<screen>&prompt.root; <userinput>zpool status -x</userinput></screen>
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<para>If all pools are healthy and everything is normal, the
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following message will be returned:</para>
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<screen>all pools are healthy</screen>
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<para>If there is an issue, perhaps a disk has gone offline,
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the pool state will look similar to:</para>
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<screen> pool: storage
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state: DEGRADED
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status: One or more devices has been taken offline by the administrator.
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Sufficient replicas exist for the pool to continue functioning in a
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degraded state.
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action: Online the device using 'zpool online' or replace the device with
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'zpool replace'.
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scrub: none requested
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config:
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|
|
|
NAME STATE READ WRITE CKSUM
|
|
storage DEGRADED 0 0 0
|
|
raidz1 DEGRADED 0 0 0
|
|
da0 ONLINE 0 0 0
|
|
da1 OFFLINE 0 0 0
|
|
da2 ONLINE 0 0 0
|
|
|
|
errors: No known data errors</screen>
|
|
|
|
<para>This indicates that the device was previously taken
|
|
offline by the administrator using the following
|
|
command:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zpool offline storage da1</userinput></screen>
|
|
|
|
<para>It is now possible to replace
|
|
<filename>da1</filename> after the system has been
|
|
powered down. When the system is back online, the following
|
|
command may issued to replace the disk:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zpool replace storage da1</userinput></screen>
|
|
|
|
<para>From here, the status may be checked again, this time
|
|
without the <option>-x</option> flag to get state
|
|
information:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zpool status storage</userinput>
|
|
pool: storage
|
|
state: ONLINE
|
|
scrub: resilver completed with 0 errors on Sat Aug 30 19:44:11 2008
|
|
config:
|
|
|
|
NAME STATE READ WRITE CKSUM
|
|
storage ONLINE 0 0 0
|
|
raidz1 ONLINE 0 0 0
|
|
da0 ONLINE 0 0 0
|
|
da1 ONLINE 0 0 0
|
|
da2 ONLINE 0 0 0
|
|
|
|
errors: No known data errors</screen>
|
|
|
|
<para>As shown from this example, everything appears to be
|
|
normal.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Data Verification</title>
|
|
|
|
<para><acronym>ZFS</acronym> uses checksums to verify the
|
|
integrity of stored data. These are enabled automatically
|
|
upon creation of file systems and may be disabled using the
|
|
following command:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set checksum=off storage/home</userinput></screen>
|
|
|
|
<para>Doing so is <emphasis>not</emphasis> recommended as
|
|
checksums take very little storage space and are used to
|
|
check data integrity using checksum verification in a
|
|
process is known as <quote>scrubbing.</quote> To verify the
|
|
data integrity of the <literal>storage</literal> pool, issue
|
|
this command:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zpool scrub storage</userinput></screen>
|
|
|
|
<para>This process may take considerable time depending on
|
|
the amount of data stored. It is also very
|
|
<acronym>I/O</acronym> intensive, so much so that only one
|
|
scrub may be run at any given time. After the scrub has
|
|
completed, the status is updated and may be viewed by
|
|
issuing a status request:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zpool status storage</userinput>
|
|
pool: storage
|
|
state: ONLINE
|
|
scrub: scrub completed with 0 errors on Sat Jan 26 19:57:37 2013
|
|
config:
|
|
|
|
NAME STATE READ WRITE CKSUM
|
|
storage ONLINE 0 0 0
|
|
raidz1 ONLINE 0 0 0
|
|
da0 ONLINE 0 0 0
|
|
da1 ONLINE 0 0 0
|
|
da2 ONLINE 0 0 0
|
|
|
|
errors: No known data errors</screen>
|
|
|
|
<para>The completion time is displayed and helps to ensure
|
|
data integrity over a long period of time.</para>
|
|
|
|
<para>Refer to &man.zfs.8; and &man.zpool.8; for other
|
|
<acronym>ZFS</acronym> options.</para>
|
|
</sect3>
|
|
|
|
<sect3 xml:id="zfs-quotas">
|
|
<title>ZFS Quotas</title>
|
|
|
|
<para>ZFS supports different types of quotas: the refquota,
|
|
the general quota, the user quota, and the group quota.
|
|
This section explains the basics of each type and includes
|
|
some usage instructions.</para>
|
|
|
|
<para>Quotas limit the amount of space that a dataset and its
|
|
descendants can consume, and enforce a limit on the amount
|
|
of space used by file systems and snapshots for the
|
|
descendants. Quotas are useful to limit the amount of space
|
|
a particular user can use.</para>
|
|
|
|
<note>
|
|
<para>Quotas cannot be set on volumes, as the
|
|
<literal>volsize</literal> property acts as an implicit
|
|
quota.</para>
|
|
</note>
|
|
|
|
<para>The
|
|
<literal>refquota=<replaceable>size</replaceable></literal>
|
|
limits the amount of space a dataset can consume by
|
|
enforcing a hard limit on the space used. However, this
|
|
hard limit does not include space used by descendants, such
|
|
as file systems or snapshots.</para>
|
|
|
|
<para>To enforce a general quota of 10 GB for
|
|
<filename>storage/home/bob</filename>, use the
|
|
following:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set quota=10G storage/home/bob</userinput></screen>
|
|
|
|
<para>User quotas limit the amount of space that can be used
|
|
by the specified user. The general format is
|
|
<literal>userquota@<replaceable>user</replaceable>=<replaceable>size</replaceable></literal>,
|
|
and the user's name must be in one of the following
|
|
formats:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><acronym
|
|
role="Portable Operating System
|
|
Interface">POSIX</acronym> compatible name such as
|
|
<replaceable>joe</replaceable>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><acronym
|
|
role="Portable Operating System
|
|
Interface">POSIX</acronym> numeric ID such as
|
|
<replaceable>789</replaceable>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><acronym role="System Identifier">SID</acronym> name
|
|
such as
|
|
<replaceable>joe.bloggs@example.com</replaceable>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><acronym role="System Identifier">SID</acronym>
|
|
numeric ID such as
|
|
<replaceable>S-1-123-456-789</replaceable>.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>For example, to enforce a quota of 50 GB for a user
|
|
named <replaceable>joe</replaceable>, use the
|
|
following:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set userquota@joe=50G</userinput></screen>
|
|
|
|
<para>To remove the quota or make sure that one is not set,
|
|
instead use:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set userquota@joe=none</userinput></screen>
|
|
|
|
<para>User quota properties are not displayed by
|
|
<command>zfs get all</command>.
|
|
Non-<systemitem class="username">root</systemitem> users can
|
|
only see their own quotas unless they have been granted the
|
|
<literal>userquota</literal> privilege. Users with this
|
|
privilege are able to view and set everyone's quota.</para>
|
|
|
|
<para>The group quota limits the amount of space that a
|
|
specified group can consume. The general format is
|
|
<literal>groupquota@<replaceable>group</replaceable>=<replaceable>size</replaceable></literal>.</para>
|
|
|
|
<para>To set the quota for the group
|
|
<replaceable>firstgroup</replaceable> to 50 GB,
|
|
use:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set groupquota@firstgroup=50G</userinput></screen>
|
|
|
|
<para>To remove the quota for the group
|
|
<replaceable>firstgroup</replaceable>, or to make sure that
|
|
one is not set, instead use:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set groupquota@firstgroup=none</userinput></screen>
|
|
|
|
<para>As with the user quota property,
|
|
non-<systemitem class="username">root</systemitem> users can
|
|
only see the quotas associated with the groups that they
|
|
belong to. However, <systemitem
|
|
class="username">root</systemitem> or a user with the
|
|
<literal>groupquota</literal> privilege can view and set all
|
|
quotas for all groups.</para>
|
|
|
|
<para>To display the amount of space consumed by each user on
|
|
the specified file system or snapshot, along with any
|
|
specified quotas, use <command>zfs userspace</command>.
|
|
For group information, use <command>zfs
|
|
groupspace</command>. For more information about
|
|
supported options or how to display only specific options,
|
|
refer to &man.zfs.1;.</para>
|
|
|
|
<para>Users with sufficient privileges and <systemitem
|
|
class="username">root</systemitem> can list the quota for
|
|
<filename>storage/home/bob</filename> using:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs get quota storage/home/bob</userinput></screen>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>ZFS Reservations</title>
|
|
|
|
<para>ZFS supports two types of space reservations. This
|
|
section explains the basics of each and includes some usage
|
|
instructions.</para>
|
|
|
|
<para>The <literal>reservation</literal> property makes it
|
|
possible to reserve a minimum amount of space guaranteed
|
|
for a dataset and its descendants. This means that if a
|
|
10 GB reservation is set on
|
|
<filename>storage/home/bob</filename>, if disk
|
|
space gets low, at least 10 GB of space is reserved
|
|
for this dataset. The <literal>refreservation</literal>
|
|
property sets or indicates the minimum amount of space
|
|
guaranteed to a dataset excluding descendants, such as
|
|
snapshots. As an example, if a snapshot was taken of
|
|
<filename>storage/home/bob</filename>, enough disk space
|
|
would have to exist outside of the
|
|
<literal>refreservation</literal> amount for the operation
|
|
to succeed because descendants of the main data set are
|
|
not counted by the <literal>refreservation</literal>
|
|
amount and so do not encroach on the space set.</para>
|
|
|
|
<para>Reservations of any sort are useful in many situations,
|
|
such as planning and testing the suitability of disk space
|
|
allocation in a new system, or ensuring that enough space is
|
|
available on file systems for system recovery procedures and
|
|
files.</para>
|
|
|
|
<para>The general format of the <literal>reservation</literal>
|
|
property is
|
|
<literal>reservation=<replaceable>size</replaceable></literal>,
|
|
so to set a reservation of 10 GB on
|
|
<filename>storage/home/bob</filename>, use:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set reservation=10G storage/home/bob</userinput></screen>
|
|
|
|
<para>To make sure that no reservation is set, or to remove a
|
|
reservation, use:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs set reservation=none storage/home/bob</userinput></screen>
|
|
|
|
<para>The same principle can be applied to the
|
|
<literal>refreservation</literal> property for setting a
|
|
refreservation, with the general format
|
|
<literal>refreservation=<replaceable>size</replaceable></literal>.</para>
|
|
|
|
<para>To check if any reservations or refreservations exist on
|
|
<filename>storage/home/bob</filename>, execute one of the
|
|
following commands:</para>
|
|
|
|
<screen>&prompt.root; <userinput>zfs get reservation storage/home/bob</userinput>
|
|
&prompt.root; <userinput>zfs get refreservation storage/home/bob</userinput></screen>
|
|
</sect3>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 xml:id="filesystems-linux">
|
|
<title>&linux; File Systems</title>
|
|
|
|
<para>&os; provides built-in support for several &linux; file
|
|
systems. This section demonstrates how to load support for and
|
|
how to mount the supported &linux; file systems.</para>
|
|
|
|
<sect2>
|
|
<title><acronym>ext2</acronym></title>
|
|
|
|
<para>Kernel support for ext2 file systems has
|
|
been available since &os; 2.2. In &os; 8.x and
|
|
earlier, the code is licensed under the
|
|
<acronym>GPL</acronym>. Since &os; 9.0, the code has
|
|
been rewritten and is now <acronym>BSD</acronym>
|
|
licensed.</para>
|
|
|
|
<para>The &man.ext2fs.5; driver allows the &os; kernel to both
|
|
read and write to ext2 file systems.</para>
|
|
|
|
<note>
|
|
<para>
|
|
This driver can also be used to access ext3 and ext4 file
|
|
systems. However, ext3 journaling, extended attributes, and
|
|
inodes greater than 128-bytes are not supported. Support
|
|
for ext4 is read-only.</para>
|
|
</note>
|
|
|
|
<para>To access an ext file system, first
|
|
load the kernel loadable module:</para>
|
|
|
|
<screen>&prompt.root; <userinput>kldload ext2fs</userinput></screen>
|
|
|
|
<para>Then, mount the ext volume by specifying its &os;
|
|
partition name and an existing mount point. This example
|
|
mounts <filename>/dev/ad1s1</filename> on
|
|
<filename>/mnt</filename>:</para>
|
|
|
|
<screen>&prompt.root; <userinput>mount -t ext2fs <replaceable>/dev/ad1s1</replaceable> <replaceable>/mnt</replaceable></userinput></screen>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>XFS</title>
|
|
|
|
<para>A &os; kernel can be configured to provide read-only
|
|
support for <acronym>XFS</acronym>
|
|
file systems.</para>
|
|
|
|
<para>To compile in <acronym>XFS</acronym> support, add the
|
|
following option to a custom kernel configuration file and
|
|
recompile the kernel using the instructions in <xref
|
|
linkend="kernelconfig"/>:</para>
|
|
|
|
<programlisting>options XFS</programlisting>
|
|
|
|
<para>Then, to mount an <acronym>XFS</acronym> volume located on
|
|
<filename>/dev/ad1s1</filename>:</para>
|
|
|
|
<screen>&prompt.root; <userinput>mount -t xfs <replaceable>/dev/ad1s1</replaceable> <replaceable>/mnt</replaceable></userinput></screen>
|
|
|
|
<para>The <package>sysutils/xfsprogs</package> package or
|
|
port provides additional
|
|
utilities, with man pages, for using, analyzing, and repairing
|
|
<acronym>XFS</acronym> file systems.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>ReiserFS</title>
|
|
|
|
<para>&os; provides read-only support for The Reiser file
|
|
system, ReiserFS.</para>
|
|
|
|
<para>To load the &man.reiserfs.5; driver:</para>
|
|
|
|
<screen>&prompt.root; <userinput>kldload reiserfs</userinput></screen>
|
|
|
|
<para>Then, to mount a ReiserFS volume located on
|
|
<filename>/dev/ad1s1</filename>:</para>
|
|
|
|
<screen>&prompt.root; <userinput>mount -t reiserfs <replaceable>/dev/ad1s1</replaceable> <replaceable>/mnt</replaceable></userinput></screen>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<!--
|
|
<sect1>
|
|
<title>Device File System</title>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>DOS and NTFS File Systems</title>
|
|
<para>This is a good section for those who transfer files, using
|
|
USB devices, from Windows to FreeBSD and vice-versa. My camera,
|
|
and many other cameras I have seen default to using FAT16. There
|
|
is (was?) a kde utility, I think called kamera, that could be used
|
|
to access camera devices. A section on this would be useful.</para>
|
|
|
|
<para>XXXTR: Though! The disks chapter, covers a bit of this and
|
|
devfs under it's USB devices. It leaves a lot to be desired though,
|
|
see:
|
|
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/usb-disks.html
|
|
It may be better to flesh out that section a bit more. Add the
|
|
word "camera" to it so that others can easily notice.</para>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>Linux EXT File System</title>
|
|
|
|
<para>Probably NOT as useful as the other two, but it requires
|
|
knowledge of the existence of the tools. Which are hidden in
|
|
the ports collection. Most Linux guys would probably only use
|
|
Linux, BSD guys would be smarter and use NFS.</para>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>HFS</title>
|
|
|
|
<para>I think this is the file system used on Apple OSX. There are
|
|
tools in the ports collection, and with Apple being a big
|
|
FreeBSD supporter and user of our technologies, surely there
|
|
is enough cross over to cover this?</para>
|
|
</sect1>
|
|
-->
|
|
|
|
</chapter>
|