ZPOOL-SCRUB(8)          FreeBSD System Manager's Manual         ZPOOL-SCRUB(8)

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

SYNOPSIS
     zpool scrub [-s|-p] [-w] 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     that resilvering only examines data that ZFS knows to be out of date (for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.

     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 again.

     -w  Wait until scrub has completed before returning.

EXAMPLES
     Example 1: Status of pool with ongoing scrub:
           Output:
                 # 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.

PERIODIC SCRUB
     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 --now

             systemctl enable zfs-scrub-monthly@otherpool.timer --now

SEE ALSO
     systemd.timer(5), zpool-iostat(8), zpool-resilver(8), zpool-status(8)

FreeBSD 13.1-RELEASE-p6          July 25, 2021         FreeBSD 13.1-RELEASE-p6