Creating a ZFS Storage Pool with Cache Devices

You can create a storage pool with cache devices to cache storage pool data. For example:

# zpool create tank mirror c2t0d0 c2t1d0 c2t3d0 cache c2t5d0 c2t8d0
# zpool status tank
  pool: tank
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            c2t0d0  ONLINE       0     0     0
            c2t1d0  ONLINE       0     0     0
            c2t3d0  ONLINE       0     0     0
        cache
          c2t5d0    ONLINE       0     0     0
          c2t8d0    ONLINE       0     0     0

errors: No known data errors

Review the following points when considering whether to create a ZFS storage pool with cache devices:

• Using cache devices provide the greatest performance improvement for random read-workloads of mostly static content.

• Capacity and reads can be monitored by using the zpool iostat command.

• Single or multiple cache devices can be added when the pool is created or added and removed after the pool is created. For more information, see Example 4–4.

• Cache devices cannot be mirrored or be part of a RAID-Z configuration.

• If a read error is encountered on a cache device, that read I/O is reissued to the original storage pool device, which might be part of a mirrored or RAID-Z configuration. The content of the cache devices is considered volatile, as is the case with other system caches.