Attaching and Detaching Devices in a Storage Pool

In addition to the zpool add command, you can use the zpool attach command to add a new device to an existing mirrored or nonmirrored device.

If you are attaching a disk to create a mirrored root pool, see How to Configure a Mirrored Root Pool (SPARC or x86/VTOC).

If you are replacing a disk in a ZFS root pool, see How to Replace a Disk in a ZFS Root Pool (SPARC or x86/VTOC).

Example 3-5  Converting a Two-Way Mirrored Storage Pool to a Three-way Mirrored Storage Pool

In this example, zeepool is an existing two-way mirror that is converted to a three-way mirror by attaching c2t1d0, the new device, to the existing device, c1t1d0.

# zpool status zeepool
pool: zeepool
state: ONLINE
scrub: none requested
config:

NAME           STATE     READ  WRITE  CKSUM
zeepool        ONLINE       0      0      0
   mirror-0    ONLINE       0      0      0
      c0t1d0   ONLINE       0      0      0
      c1t1d0   ONLINE       0      0      0

errors: No known data errors
# zpool attach zeepool c1t1d0 c2t1d0
# zpool status zeepool
pool: zeepool
state: ONLINE
scrub: resilver completed after 0h0m with 0 errors on Fri Jan  8 12:59:20 2010
config:

NAME           STATE     READ  WRITE  CKSUM
zeepool        ONLINE       0      0      0
   mirror-0    ONLINE       0      0      0
      c0t1d0   ONLINE       0      0      0
      c1t1d0   ONLINE       0      0      0
      c2t1d0   ONLINE       0      0      0  592K resilvered

errors: No known data errors

If the existing device is part of a three-way mirror, attaching the new device creates a four-way mirror, and so on. Whatever the case, the new device begins to resilver immediately.

Example 3-6  Converting a Nonredundant ZFS Storage Pool to a Mirrored ZFS Storage Pool

In addition, you can convert a nonredundant storage pool to a redundant storage pool by using the zpool attach command. For example:

# zpool create tank c0t1d0
# zpool status tank
pool: tank
state: ONLINE
scrub: none requested
config:
NAME           STATE     READ  WRITE  CKSUM
tank          ONLINE        0      0      0
c0t1d0        ONLINE       0      0      0

errors: No known data errors
# zpool attach tank c0t1d0 c1t1d0
# zpool status tank
pool: tank
state: ONLINE
scrub: resilver completed after 0h0m with 0 errors on Fri Jan  8 14:28:23 2010
config:

NAME           STATE     READ  WRITE  CKSUM
tank           ONLINE       0      0      0
   mirror-0    ONLINE       0      0      0
      c0t1d0   ONLINE       0      0      0
      c1t1d0   ONLINE       0      0      0  73.5K resilvered

errors: No known data errors

You can use the zpool detach command to detach a device from a mirrored storage pool. For example:

# zpool detach zeepool c2t1d0

However, this operation fails if no other valid replicas of the data exist. For example:

# zpool detach newpool c1t2d0
cannot detach c1t2d0: only applicable to mirror and replacing vdevs