raid6check(8) — Linux manual page

NAME \| SYNOPSIS \| DESCRIPTION \| EXAMPLES \| FILES \| BUGS \| COLOPHON

RAID6CHECK(8)            System Manager's Manual            RAID6CHECK(8)

NAME top

       raid6check - check MD RAID6 device for errors aka Linux Software
       RAID

SYNOPSIS top

       raid6check <raid6_device> <start_stripe> <number_of_stripes>
       [autorepair]

       raid6check <raid6_device> repair <stripe> <failed_slot_1>
       <failed_slot_2>

DESCRIPTION top

       RAID6 devices in which one single component drive has errors can
       use the double parity in order to find out which component drive.
       The "raid6check" tool has two modes: check mode and repair mode.

       "raid6check" requires a non-degraded RAID6 MD device as first
       parameter. If the given MD device is not a RAID6, "raid6check"
       will, of course, not continue.

       If the RAID6 MD device is degraded, "raid6check" will report an
       error and it will not proceed further.

   Check mode
       In the check mode, the "raid6check" tool checks, for each stripe,
       the double parity consistency, reports mismatches and, if
       possible, which component drive has the mismatch.  Since it works
       at stripe level, it can report different drives with mismatches at
       different stripes.

       In addition to the MD device, "raid6check" requries a starting
       stripe (usually 0) and the number of stripes to be checked.  If
       this third parameter is also 0, it will check the array up to the
       end.  If the fourth parameter is "autorepair", it will overwrite
       single-slot errors.

       "raid6check" will start printing information about the RAID6, then
       for each stripe, it will report the parity rotation status.  In
       case of parity mismatches, "raid6check" reports, if possible,
       which component drive could be responsible.  Otherwise it reports
       that it is not possible to find the component drive.

       No write operations are performed on the array or the components,
       unless "autorepair" is specified.  Furthermore, the checked array
       can be online and in use during the operation of "raid6check".

   Repair mode
       In the repair mode, the "raid6check" tool checks the given stripe.
       If inconsistencies are found, it attempts to repair the strip
       assuming that the two given slots are incorrect.

       -1 may be used to specify parity P and -2 parity Q.

EXAMPLES top

         raid6check /dev/md0 0 0
       This will check /dev/md0 from start to end.

         raid6check /dev/md3 0 1 autorepair
       This will check the first stripe of /dev/md3.  Any error will be
       reported, and if single-slot, repaired.

         raid6check /dev/md3 0 repair 1 -1 -2
       This will check the first stripe of /dev/md3.  If any
       inconsistencies are found, repair is performed assuming the two
       parities are incorrect.

         raid6check /dev/md1 1000 0
       This will check /dev/md1 from stripe 1000 up to the end.

         raid6check /dev/m127 128 256
       This will check 256 stripes of /dev/md127 starting from stripe
       128.

         raid6check /dev/md0 0 0 | grep -i error > md0_err.log
       This will check /dev/md0 completely and create a log file only
       with errors, if any.

FILES top

       "raid6check" uses directly the component drives as found in /dev.
       Furthermore, the sysfs interface is needed in order to find out
       the RAID6 parameters.

BUGS top

       Negative stripe parameters can lead to unexpected results due to
       strtoull.  (Negative slot numbers should work for Q [-1] and P
       [-2] but currently involve compiler-defined behavior.)

       It is not clear what will happen if the RAID6 MD device gets
       degraded during the check.

       The latest version of raid6check should always be available from

              https://www.kernel.org/pub/linux/utils/raid/mdadm/ 

       Related man pages:

       mdadm(8) mdmon(8), mdadm.conf(5), md(4).

COLOPHON top

       This page is part of the mdadm (Tool for managing md arrays in
       Linux) project.  Information about the project can be found at 
       ⟨http://neil.brown.name/blog/mdadm⟩.  If you have a bug report for
       this manual page, send it to linux-raid@vger.kernl.org.  This page
       was obtained from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/⟩ on
       2026-01-16.  (At that time, the date of the most recent commit
       that was found in the repository was 2025-12-16.)  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a
       mail to man-pages@man7.org

v1.0.0                                                      RAID6CHECK(8)