From f95372cee11b460232c57befb03ce971fd5a485a Mon Sep 17 00:00:00 2001 From: Daniel Gerzo Date: Mon, 6 Feb 2012 17:13:58 +0000 Subject: [PATCH] - add a section covering graid3 PR: docs/164228 Submitted by: Mark Gladman Reviewed by: wblock, bcr --- .../books/handbook/geom/chapter.sgml | 163 ++++++++++++++++++ 1 file changed, 163 insertions(+) diff --git a/en_US.ISO8859-1/books/handbook/geom/chapter.sgml b/en_US.ISO8859-1/books/handbook/geom/chapter.sgml index a5a0b22e5f..cf3b0065b3 100644 --- a/en_US.ISO8859-1/books/handbook/geom/chapter.sgml +++ b/en_US.ISO8859-1/books/handbook/geom/chapter.sgml @@ -440,6 +440,169 @@ OK? boot + + + + + Mark + Gladman + Written by + + + Daniel + Gerzo + + + + + Tom + Rhodes + Based on documentation by + + + Murray + Stokely + + + + + + GEOM + + + RAID3 + + + <acronym>RAID</acronym>3 - Byte-level Striping with Dedicated + Parity + + RAID3 is a method used to combine several + disk drives into a single volume with a dedicated parity + disk. In a RAID3 system, data is split up + into a number of bytes that are written across all the drives in + the array except for one disk which acts as a dedicated parity + disk. This means that reading 1024KB from a + RAID3 implementation will access all disks in + the array. Performance can be enhanced by using multiple + disk controllers. The RAID3 array provides a + fault tolerance of 1 drive, while providing a capacity of 1 - 1/n + times the total capacity of all drives in the array, where n is the + number of hard drives in the array. Such a configuration is + mostly suitable for storing data of larger sizes, e.g. + multimedia files. + + At least 3 physical hard drives are required to build a + RAID3 array. Each disk must be of the same + size, since I/O requests are interleaved to read or write to + multiple disks in parallel. Also, due to the nature of + RAID3, the number of drives must be + equal to 3, 5, 9, 17, etc. (2^n + 1). + + + Creating a Dedicated <acronym>RAID</acronym>3 Array + + In &os;, support for RAID3 is + implemented by the &man.graid3.8; GEOM + class. Creating a dedicated + RAID3 array on &os; requires the following + steps. + + + While it is theoretically possible to boot from a + RAID3 array on &os;, that configuration + is uncommon and is not advised. + + + + + First, load the geom_raid3.ko + kernel module by issuing the following command: + + &prompt.root; graid3 load + + Alternatively, it is possible to manually load the + geom_raid3.ko module: + + &prompt.root; kldload geom_raid3.ko + + + + Create or ensure that a suitable mount point + exists: + + &prompt.root; mkdir /multimedia/ + + + + Determine the device names for the disks which will be + added to the array, and create the new + RAID3 device. The final device listed + will act as the dedicated parity disk. This + example uses three unpartitioned + ATA drives: + ada1 + and ada2 + for data, and + ada3 + for parity. + + &prompt.root; graid3 label -v gr0 /dev/ada1 /dev/ada2 /dev/ada3 +Metadata value stored on /dev/ada1. +Metadata value stored on /dev/ada2. +Metadata value stored on /dev/ada3. +Done. + + + + Partition the newly created + gr0 device and put a UFS file + system on it: + + &prompt.root; gpart create -s GPT /dev/raid3/gr0 +&prompt.root; gpart add -t freebsd-ufs /dev/raid3/gr0 +&prompt.root; newfs -j /dev/raid3/gr0p1 + + Many numbers will glide across the screen, and after a + bit of time, the process will be complete. The volume has + been created and is ready to be mounted. + + + + The last step is to mount the file system: + + &prompt.root; mount /dev/raid3/gr0p1 /multimedia/ + + The RAID3 array is now ready to + use. + + + + Additional configuration is needed to retain the above + setup across system reboots. + + + + The geom_raid3.ko module must be + loaded before the array can be mounted. To automatically + load the kernel module during the system initialization, add + the following line to the + /boot/loader.conf file: + + geom_raid3_load="YES" + + + + The following volume information must be added to the + /etc/fstab file in order to + automatically mount the array's file system during + the system boot process: + + /dev/raid3/gr0p1 /multimedia ufs rw 2 2 + + + + + GEOM Gate Network Devices