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Have you ever wanted to experiment with zfs, but didn't have a storage array on hand? No worries - use files instead of disks to build your zfs test configuration.

With this approach, you can construct complex zfs configurations consisting of large numbers of 'pseudo-disks' to test a zfs configuration, recovery scenario, hot sparing, or to familiarize yourself with the zfs feature set - file system creation, snapshots, clones ...

zfs storage pools can be constructed from whole disks, disk slices, or individual files. Use files (created using the 'mkfile' command) to build your zfs mirror, raidz or raidz2 test configurations.

For example, to create a zfs mirror using files instead of devices:
- Create two 100 megabyte files
# (cd /export; mkfile 100m file1 file2)
- Add the files to a zfs pool as a mirrored pair
# zpool create mymirror mirror /export/file1 /export/file2

Similarly for raidz
# (cd /export; mkfile 100m raidz1 raidz2 raidz3)
# zpool create myraidz raidz /export/raidz1 /export/raidz2 /export/raidz3

And raidz2
# (cd /export; mkfile 100m raidz21 raidz22 raidz23 raidz24)
# zpool create myraidz2 raidz2 /export/raidz21 /export/raidz22 /export/raidz23 /export/raidz24

Add a hot spare to raidz2:
# mkfile 100m /export/hotspare
# zpool add myraidz2 spare /export/hotspare

Display your pools
# zpool list
NAME        SIZE   USED  AVAIL    CAP  HEALTH  ALTROOT
mymirror   95.5M   111K  95.4M     0%  ONLINE  -
myraidz     286M   155K   286M     0%  ONLINE  -
myraidz2    382M   288K   382M     0%  ONLINE  -


Enjoy experimenting with zfs !