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Solaris ZFS Administration Guide

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 non-mirrored device.

If you are adding and detaching a disk in a ZFS root pool to replace a disk, see How to Replace a Disk in the ZFS Root Pool.

Example 4–5 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 transformed 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 two-way mirror, attaching the new device, creates a three-way mirror, and so on. In either case, the new device begins to resilver immediately.

Example 4–6 Converting a Non-Redundant ZFS Storage Pool to a Mirrored ZFS Storage Pool

In addition, you can convert a non-redundant storage pool into 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 is refused if there are no other valid replicas of the data. For example: 


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