Oracle Solaris ZFS Administration Guide

Bringing a Device Online

After a device is taken offline, it can be brought online again by using the zpool online command. For example:

# zpool online tank c1t0d0
bringing device c1t0d0 online

When a device is brought online, any data that has been written to the pool is resynchronized with the newly available device. Note that you cannot use bring a device online to replace a disk. If you take a device offline, replace the device, and try to bring it online, it remains in the faulted state.

If you attempt to bring online a faulted device, a message similar to the following is displayed:

# zpool online tank c1t0d0
warning: device 'c1t0d0' onlined, but remains in faulted state
use 'zpool replace' to replace devices that are no longer present

You might also see the faulted disk message displayed on the console or written to the /var/adm/messages file. For example:

SUNW-MSG-ID: ZFS-8000-D3, TYPE: Fault, VER: 1, SEVERITY: Major
EVENT-TIME: Wed Jun 30 14:53:39 MDT 2010
PLATFORM: SUNW,Sun-Fire-880, CSN: -, HOSTNAME: neo
SOURCE: zfs-diagnosis, REV: 1.0
EVENT-ID: 504a1188-b270-4ab0-af4e-8a77680576b8
DESC: A ZFS device failed.  Refer to for more information.
AUTO-RESPONSE: No automated response will occur.
IMPACT: Fault tolerance of the pool may be compromised.
REC-ACTION: Run 'zpool status -x' and replace the bad device.

For more information about replacing a faulted device, see Resolving a Missing Device.

You can use the zpool online -e command to expand the pool's size when a smaller disk is replaced by a larger disk. By default, pool size is not expanded to its full size unless the autoexpand pool property is enabled. You can expand the pool size automatically when a smaller disk is replaced by a larger disk by using the zpool online -ecommand even if the disk is already online or if the disk is currently offline. For example:

# zpool online -e tank c1t13d0