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>

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 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.

       "raid6check" requires a non-degraded RAID6 MD device as first
       parameter, 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.

       "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.

       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.

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

EXAMPLES         top

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

         raid6check /dev/md3 0 1
       This will check the first stripe of /dev/md3.

         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 parameters can lead to unexpected results.

       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


       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 
       ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page
       was obtained from the project's upstream Git repository
       ⟨⟩ on
       2020-02-08.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-01-21.)  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

v1.0.0                                                         RAID6CHECK(8)