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,
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".
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.
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 firstname.lastname@example.org. This page
was obtained from the project's upstream Git repository
⟨git://neil.brown.name/mdadm⟩ on 2017-03-13. If you discover any ren‐
dering 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