Determining If a Device Can Be Replaced

For a device to be replaced, the pool must be in the ONLINE state. The device must be part of a redundant configuration, or it must be healthy (in the ONLINE state). If the device is part of a redundant configuration, sufficient replicas from which to retrieve good data must exist. If two disks in a four-way mirror are faulted, then either disk can be replaced because healthy replicas are available. However, if two disks in a four-way RAID-Z (raidz1) virtual device are faulted, then neither disk can be replaced because insufficient replicas from which to retrieve data exist. If the device is damaged but otherwise online, it can be replaced as long as the pool is not in the FAULTED state. However, any corrupted data on the device is copied to the new device, unless sufficient replicas with good data exist.

In the following configuration, the c1t1d0 disk can be replaced, and any data in the pool is copied from the healthy replica, c1t0d0:

    mirror            DEGRADED
    c1t0d0             ONLINE
    c1t1d0             FAULTED

The c1t0d0 disk can also be replaced, though no self-healing of data can take place because no good replica is available.

In the following configuration, neither faulted disk can be replaced. The ONLINE disks cannot be replaced either because the pool itself is faulted.

    raidz              FAULTED
    c1t0d0             ONLINE
    c2t0d0             FAULTED
    c3t0d0             FAULTED
    c4t0d0             ONLINE

In the following configuration, either top-level disk can be replaced, though any bad data present on the disk is copied to the new disk.

c1t0d0         ONLINE
c1t1d0         ONLINE

If either disk is faulted, then no replacement can be performed because the pool itself is faulted.