== Summary ==
ZFS filesystems are built on top of virtual storage pools called zpools. A zpool is constructed of virtual devices (vdevs), which are themselves constructed of block devices: files, hard drive partitions, or entire drives, with the last being the recommended usage.[6] Block devices within a vdev may be configured in different ways, depending on needs and space available: non-redundantly (similar to RAID 0), as a mirror (RAID 1) of two or more devices, as a RAID-Z group of three or more devices, or as a RAID-Z2 group of four or more devices.[7] Besides standard storage, devices can be designated as volatile read cache (ARC), nonvolatile write cache, or as a spare disk for use only in the case of a failure. Finally, when mirroring, block devices can be grouped according to physical chassis, so that the filesystem can continue in the face of the failure of an entire chassis.
== ZPool Types ==
'''ZPool Stripe group:'''
{{{
zpool create vol0 /dev/sda /dev/sdb /dev/sdc
}}}
'''ZPool mirror group:'''
{{{
zpool create vol0 mirror /dev/sda /dev/sdb
}}}
'''ZPool raidz group:''' Similar to RAID5.
{{{
zpool create vol0 raidz /dev/sda /dev/sdb /dev/sdc
}}}
'''ZPool raidz2 set:''' Similar to RAID5 with dual parity.
{{{
zpool create vol0 raidz2 /dev/sdb /dev/sdc1 /dev/sdd /dev/sde
}}}
== Status of the ZPool Storage ==
'''Checking the size and usage of zpools:''' zpool list
This will display something like:
{{{
root@ubuntu:~# zpool list
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
vol0 29.8G 230K 29.7G 0% ONLINE -
}}}
'''Checking health status for ZPools:''' zpool status
This will display something like:
{{{
root@ubuntu:~# zpool status
pool: vol0
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
vol0 ONLINE 0 0 0
raidz2 ONLINE 0 0 0
sdb ONLINE 0 0 0
sdc ONLINE 0 0 0
sdd ONLINE 0 0 0
spares
sde AVAIL
errors: No known data errors
}}}
'''Checking I/O statistics for ZPools:''' zpool iostat
This will display something like:
{{{
root@ubuntu:~# zpool iostat
capacity operations bandwidth
pool used avail read write read write
---------- ----- ----- ----- ----- ----- -----
vol0 230K 29.7G 0 0 10 431
}}}
More detailed view can be seen by adding the -v to the end of the '''zpool iostat'''.
{{{
root@ubuntu:~# zpool iostat -v
capacity operations bandwidth
pool used avail read write read write
---------- ----- ----- ----- ----- ----- -----
vol0 230K 29.7G 0 0 12 518
raidz2 230K 29.7G 0 0 12 518
sdb - - 0 1 274 3.41K
sdc - - 0 1 174 3.41K
sdd - - 0 0 274 3.41K
---------- ----- ----- ----- ----- ----- -----
}}}
== Adding Aditional Storage to a ZPool ==
'''Adding a spare:'''
{{{
zpool add vol0 spare /dev/sde
}}}
This will add a spare drive to be used as a hot spare in event that one of the drives in the zpool fails.
{{{
root@ubuntu:~# zpool status -v
pool: vol0
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
vol0 ONLINE 0 0 0
raidz2 ONLINE 0 0 0
sdb ONLINE 0 0 0
sdc ONLINE 0 0 0
sdd ONLINE 0 0 0
spares
sde AVAIL
}}}
'''Addtional storage to a MIRROR, RAIDZ or RAIDZ2 ZPool:'''
Adding additional storage to a mirror, raidz or raidz2 zpool must be done in like raid groups.
Example:
If I have a 3 drive raidz2 zpool....
{{{
root@ubuntu:~# zpool status
pool: vol0
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
vol0 ONLINE 0 0 0
raidz2 ONLINE 0 0 0
sdb ONLINE 0 0 0
sdc ONLINE 0 0 0
sdd ONLINE 0 0 0
errors: No known data errors
}}}
...additional storage must be added by introducing another 3 drive raidz2 raid group to the zpool.
{{{
zpool add vol0 raidz2 /dev/sde /dev/sdf /dev/sdg
}}}
So my vol0 zpool now looks like...
{{{
root@ubuntu:~# zpool status
pool: vol0
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
vol0 ONLINE 0 0 0
raidz2 ONLINE 0 0 0
sdb ONLINE 0 0 0
sdc ONLINE 0 0 0
sdd ONLINE 0 0 0
raidz2 ONLINE 0 0 0
sde ONLINE 0 0 0
sdf ONLINE 0 0 0
sdg ONLINE 0 0 0
errors: No known data errors
}}}
''Same is true for zpool mirror and raidz sets.''
== Deleting a ZPool ==
'''Deleting a zpool and deleting all data within the zpool:'''zpool destroy
Usage is...
{{{
zpool destroy nameofzpool
}}}
example:
{{{
zpool destroy vol0
}}}
== Removing a Zpool ==
If you have a zpool on eg a usb drive, this command will allow you to safely remove it:
{{{
zpool export nameofzpool
}}}
If you want to import the zpool again:
{{{
zpool import nameofzpool
}}}
Running zpool import with no arguments will list all available zpools.
== Creating a Zpool on a disk image ==
Though not recommended for normal use, it is possible to create a zpool on top of a file.
{{{
dd if=/dev/zero of=filename.img bs=1M count=1000
zpool create nameofzpool /absolute/path/to/filename.img
}}}
will create an image of 1GB. It is also possible to create a sparse image, to create an image that can hold 100GB:
{{{
dd if=/dev/zero of=filename.img bs=1k count=1 seek=100M
}}}