Determining If a Device Can Be Replaced
If the device to be replaced is part of a redundant configuration,
sufficient replicas from which to retrieve good data must exist. For
example, if two disks in a four-way mirror are UNAVAIL
,
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 UNAVAIL
, 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 UNAVAIL
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 UNAVAIL
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 UNAVAIL
disk can be replaced. The ONLINE
disks cannot be replaced either because the pool itself is UNAVAIL
.
raidz1 UNAVAIL c1t0d0 ONLINE c2t0d0 UNAVAIL c3t0d0 UNAVAIL 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 UNAVAIL
, then no replacement can be performed because the pool itself is UNAVAIL
.