|System Manager's Manual
attach new device to existing ZFS vdev
pool device new_device
Attaches new_device to the existing device. The behavior differs depending on if the existing device is a RAID-Z device, or a mirror/plain device.
If the existing device is a mirror or plain device (e.g. specified
mirror-7"), the new device will be
mirrored with the existing device, a resilver will be initiated, and the new
device will contribute to additional redundancy once the resilver completes.
If device is not currently part of a mirrored
configuration, device automatically transforms into a
two-way mirror of device and
new_device. If device is part of
a two-way mirror, attaching new_device creates a
three-way mirror, and so on. In either case,
new_device begins to resilver immediately and any
running scrub is cancelled.
If the existing device is a RAID-Z device (e.g. specified as
"raidz2-0"), the new device will become part
of that RAID-Z group. A "raidz expansion" will be initiated, and
once the expansion completes, the new device will contribute additional
space to the RAID-Z group. The expansion entails reading all allocated space
from existing disks in the RAID-Z group, and rewriting it to the new disks
in the RAID-Z group (including the newly added
device). Its progress can be monitored with
Data redundancy is maintained during and after the expansion. If a disk fails while the expansion is in progress, the expansion pauses until the health of the RAID-Z vdev is restored (e.g. by replacing the failed disk and waiting for reconstruction to complete). Expansion does not change the number of failures that can be tolerated without data loss (e.g. a RAID-Z2 is still a RAID-Z2 even after expansion). A RAID-Z vdev can be expanded multiple times.
After the expansion completes, old blocks retain their old
data-to-parity ratio (e.g. 5-wide RAID-Z2 has 3 data and 2 parity) but
distributed among the larger set of disks. New blocks will be written with
the new data-to-parity ratio (e.g. a 5-wide RAID-Z2 which has been expanded
once to 6-wide, has 4 data and 2 parity). However, the vdev's assumed parity
ratio does not change, so slightly less space than is expected may be
reported for newly-written blocks, according to
-s, and similar
A pool-wide scrub is initiated at the end of the expansion in order to verify the checksums of all blocks which have been copied during the expansion.
- Forces use of new_device, even if it appears to be in use. Not all devices can be overridden in this manner.
- Sets the given pool properties. See the zpoolprops(7) manual page for a list of valid properties that can be set. The only property supported at the moment is ashift.
- When attaching to a mirror or plain device, the new_device is reconstructed sequentially to restore redundancy as quickly as possible. Checksums are not verified during sequential reconstruction so a scrub is started when the resilver completes.
- Waits until new_device has finished resilvering or expanding before returning.
|June 28, 2023