Ubuntu Manpage: zpool-scrub — begin or resume scrub of ZFS storage pools

Provided by: zfsutils-linux_2.2.6-1ubuntu1.2_amd64

NAME

       zpool-scrub — begin or resume scrub of ZFS storage pools

SYNOPSIS

       zpool scrub [-s|-p] [-w] [-e] pool…

DESCRIPTION

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data that ZFS knows to be out of date (for example, when attaching a new device to a mirror or replacing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.

When scrubbing a pool with encrypted filesystems the keys do not need to be loaded. However, if the keys
are not loaded and an unrepairable checksum error is detected the file name cannot be included in the
zpool status -v verbose error report.

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.

OPTIONS

       -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 or zpool scrub -e again.

       -w  Wait until scrub has completed before returning.

       -e  Only  scrub  files  with  known  data errors as reported by zpool status -v.  The pool must have been
           scrubbed at least once with the head_errlog feature enabled to  use  this  option.   Error  scrubbing
           cannot  be run simultaneously with regular scrubbing or resilvering, nor can it be run when a regular
           scrub is paused.

EXAMPLES

   Example 1
       Status of pool with ongoing scrub:

       # zpool status
         ...
         scan: scrub in progress since Sun Jul 25 16:07:49 2021
               403M / 405M scanned at 100M/s, 68.4M / 405M issued at 10.0M/s
               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.

PERIODIC SCRUB