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       data that ZFS knows to be out of date (for example, when attaching a new device to a mirror or  replacing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

OpenZFS                                           July 25, 2021                                   ZPOOL-SCRUB(8)