ZFS: Create a raidz filesystem

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From the computer of: qmchenry (335 recipes)
Created: Jun 06, 2006     Updated: Jun 07, 2006

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ZFS supports a type of RAID-5 redundancy called raidz. This redundancy works at the ZFS pool level and affects all created filesystems in that pool. According to the Sun docs, raidz offers 'better distribution of parity [than RAID-5] and eliminates the “RAID-5 write hole” (in which data and parity become inconsistent after a power loss).' Creating RAID volumes in most volume managers (like VeritasVM) requires learning a new language describing the various components involved. ZFS requires one wee command.

Creating a raidz pool is similar to creating a normal pool. Only the addition of the 'raidz' keyword is required:

This command creates a raidz pool named 'rex' consisting of four disks. One thing that's a little different in a ZFS raidz pool versus other RAID-5 filesystems is that the reported available disk space doesn't subtract the space required by parity. Consider the following 'zfs list' output before and after creating a 10G file in a raidz filesystem.

Although the file added only 10G to the filesystem, the change in the used space is 13.4G, so the parity is reflected in the usage. Just an important thing to keep in mind as you monitor your filesystem.