Monday, December 04, 2006

ZFS Cheatsheet

The three primary goals of ZFS are:

  1. Highly scalable (128-bit) data repository
  2. Ease of administration
  3. Guaranteed on disk data integrity

Sample ZFS commands and usage


What You Do and See Why 
$ man zpool
$ man zfs
 Get familiar with command structure and options 
$ su
Password:
# cd /
# mkfile 100m disk1 disk2 disk3 disk5
# mkfile 50m disk4
# ls -l disk*
-rw------T   1 root     root     104857600 Oct  6 08:13 disk1
-rw------T   1 root     root     104857600 Oct  6 08:13 disk2
-rw------T   1 root     root     104857600 Oct  6 08:13 disk3
-rw------T   1 root     root     52428800 Oct  6 08:13 disk4
 Create some “virtual devices” or vdevs as described in the zpool documentation. These can also be real disk slices if you have them available. 
# zpool create myzfs /disk1 /disk2
# zpool list

NAME        SIZE    USED   AVAIL    CAP  HEALTH     ALTROOT
myzfs       199M    24.0K  199M     0%   FAULTED     -
 Create a storage pool and check the size and usage. 
# zpool status -v
pool: myzfs
state: FAULTED
reason: Too many devices are damaged or missing for the pool
to function.
  see: http://www.sun.com/msg/ZFS-XXXX-02
config:

       NAME                  STATUS
       /disk1                ONLINE
       /disk2                ONLINE
 Get more detailed status of the zfs storage pool. 
# zpool destroy myzfs
# zpool list
no pools available
 Destroy a zfs storage pool 
# zpool create myzfs mirror /disk1 /disk4
invalid vdev specification
use '-f' to override the following errors:
mirror contains devices of different sizes
 Attempt to create a zfs pool with different size vdevs fails. Using -f options forces it to occur but only uses space allowed by smallest device. 
# zpool create myzfs mirror /disk1 /disk2
# zpool status -v
   pool: myzfs
  state: FAULTED
reason: Too many devices are damaged or missing for the pool
to function.
    see: http://www.sun.com/msg/ZFS-XXXX-02
config:

       NAME                  STATUS
       mirror                ONLINE
            /disk1           ONLINE
            /disk2           ONLINE
 Create a mirrored pool. I’m not sure at this time why it is labeled as faulted. 
# zpool iostat 5
            capacity      operations    bandwidth
pool        used   avail  read   write  read   write
----------  -----  -----  -----  -----  -----  -----
myzfs       24.5K  99.5M  0      24     0      173
myzfs       24.5K  99.5M  0      0      0      0
myzfs       24.5K  99.5M  0      0      0      0
Get I/O statistics for the pool 
# zfs create myzfs/jim
# df -k
Filesystem   kbytes    used   avail capacity  Mounted on
...
myzfs/jim    85478     8      85470 1%        /zfs/myzfs/jim
 Create a file system and check it with standard df -k command. Note the size is 83.5 MB from a
100 MB zpool (mirrored). File systems are automatically mounted by default under the /zfs location. See the Mountpoints section of the zfs man page for more details. 
# zfs list
NAME         USED   AVAIL  REFER  MOUNTPOINT
myzfs        33.5K  83.5M   -     /zfs/myzfs
myzfs/jim    8K     83.5M   8K    /zfs/myzfs/jim
 List current zfs file systems. 
# zpool add myzfs /disk3
invalid vdev specification
use '-f' to override the following errors:
mismatched replication level: pool uses 2-way mirror
and new vdev uses 1-way file
 Attempt to add a single vdev to a mirrored set fails 
# zpool add myzfs mirror /disk3 /disk5
pool: myzfs
state: FAULTED
reason: Too many devices are damaged or missing for the pool
to function.
  see: http://www.sun.com/msg/ZFS-XXXX-02
config:

       NAME                  STATUS
       mirror                ONLINE
         /disk1                 ONLINE
         /disk2                 ONLINE
       mirror                ONLINE
         /disk3                 ONLINE
         /disk5                 ONLINE
 Add a mirrored set of vdevs 
# zfs create myzfs/jim2
# zfs list
NAME         USED   AVAIL  REFER  MOUNTPOINT
myzfs        26.5M  156M   -      /zfs/myzfs
myzfs/jim    26.3M  156M   26.3M  /zfs/myzfs/jim
myzfs/jim2   8K     156M   8K     /zfs/myzfs/jim2
 Create a second file system. Note that both file system show 156M available because no quotas are
set. Each “could” grow to file the pool. 
# zfs set reservation=20m myzfs/jim
# zfs list -o reservation
RESERV
none
20.0M
 Reserve a specified amount of space for a file system ensuring that other users don’t take up all the space. 
# zfs set quota=20m myzfs/jim2
# zfs list -o quota myzfs/jim myzfs/jim2
QUOTA
none
20.0M
 Set and view quotas 
# zfs set compression=on myzfs/jim2
# zfs list -o compression
COMPRESS
off
off
on
 Turn on compression 
# zfs snapshot myzfs/jim@test
# zfs list
NAME           USED   AVAIL  REFER  MOUNTPOINT
myzfs          20.0M  63.5M  -      /zfs/myzfs
myzfs/jim      8K     83.5M  8K     /zfs/myzfs/jim
myzfs/jim@test 0      -      8K     /zfs/myzfs/jim@test
 Create a snapshot called test. 
# zfs rollback myzfs/jim@test
 Rollback to a snapshot. 
# zfs clone myzfs/jim@test myzfs/jim3
# zfs list
NAME           USED   AVAIL  REFER  MOUNTPOINT
myzfs          20.0M  63.5M  -      /zfs/myzfs
myzfs/jim      8K     83.5M  8K     /zfs/myzfs/jim
myzfs/jim@test 0      -      8K     /zfs/myzfs/jim@test
myzfs/jim3     0      63.5M  8K     /zfs/myzfs/jim3
 A snapshot is not directly addressable. A clone must be made.The target dataset can be located anywhere in the ZFS hierarchy, and will be created as the same type as the original. 
# zfs destroy myzfs/jim2
# zfs list
NAME           USED   AVAIL  REFER  MOUNTPOINT
myzfs          26.5M  157M   -      /zfs/myzfs
myzfs/jim      26.3M  157M   26.3M  /zfs/myzfs/jim
 Destroy a filesystem 
# zpool destroy myzfs
cannot destroy 'myzfs': pool is not empty
use '-f' to force destruction anyway
 Can’t destroy a pool with active filesystems. 
# zfs unmount myzfs/jim
 Unmount a ZFS file system 
# zpool destroy -f myzfs
# zpool status -v
no pools available
 Use the -f option to destroy a pool with files systems created.
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