zpool-scrub —
begin or resume scrub of ZFS storage pools
zpool |
scrub
[-s|-p
]
[-w
]
pool… |
Begins a scrub or resumes a paused scrub. The scrub examines all data in the
specified pools to verify that it checksums correctly. For replicated (mirror,
raidz, or draid) devices, ZFS automatically repairs any damage discovered
during the scrub. The
zpool
status command reports the progress of the
scrub and summarizes the results of the scrub upon completion.
Scrubbing and resilvering are very similar operations. The difference is that
resilvering only examines data that ZFS knows to be out of date (for example,
when attaching a new device to a mirror or replacing an existing device),
whereas scrubbing examines all data to discover silent errors due to hardware
faults or disk failure.
Because scrubbing and resilvering are I/O-intensive operations, ZFS only allows
one at a time.
A scrub is split into two parts: metadata scanning and block scrubbing. The
metadata scanning sorts blocks into large sequential ranges which can then be
read much more efficiently from disk when issuing the scrub I/O.
If a scrub is paused, the
zpool
scrub resumes it. If a resilver is in
progress, ZFS does not allow a scrub to be started until the resilver
completes.
Note that, due to changes in pool data on a live system, it is possible for
scrubs to progress slightly beyond 100% completion. During this period, no
completion time estimate will be provided.
-s- Stop scrubbing.
-p- Pause scrubbing. Scrub pause state and progress are periodically synced to
disk. If the system is restarted or pool is exported during a paused
scrub, even after import, scrub will remain paused until it is resumed.
Once resumed the scrub will pick up from the place where it was last
checkpointed to disk. To resume a paused scrub issue
zpool
scrub again.
-w- Wait until scrub has completed before returning.
Example 1: Status of pool with
ongoing scrub:
# zpool status
...
scan: scrub in progress since Sun Jul 25 16:07:49 2021
403M scanned at 100M/s, 68.4M issued at 10.0M/s, 405M total
0B repaired, 16.91% done, 00:00:04 to go
...
Where metadata which references 403M of file data has been scanned at 100M/s,
and 68.4M of that file data has been scrubbed sequentially at 10.0M/s.
On machines using systemd, scrub timers can be enabled on per-pool basis.
weekly and
monthly timer units are provided.
systemctl
enable
zfs-scrub-
weekly@rpool.timer
--nowsystemctl
enable
zfs-scrub-monthly@otherpool.timer
--now
systemd.timer(5),
zpool-iostat(8),
zpool-resilver(8),
zpool-status(8)