When the UFS filesystem was introduced to BSD in 1982, its use of 32 bit offsets and counters to address the storage was considered to be ahead of its time. Since most fixed-disk storage devices use 512 byte - sectors, 32 bits allowed for 2 Terabytes of storage. That was an almost + sectors, 32 bits allowed for 2 Terabytes of storage. That was an almost un-imaginable quantity for the time. But now that 250 and 400 Gigabyte disks are available at consumer prices, it's trivial to build a hardware or software based storage array that can exceed 2TB for a few thousand @@ -92,7 +92,7 @@
Even though large drives are cheap, it still isn't always feasible or economical to test on real hardware. Swap-backed memory disks, via the - md(4) driver, can provide a good substitute for some of the testing. + md(4) driver, can provide a good substitute for some of the testing. Backing with swap means that only the pages that are dirtied by data are actually allocated, so a multi-terabyte storage can be simulated with a minimal amount of physical RAM+swap. Note that this is less true with