raid6check − check MD RAID6 device for errors aka Linux Software RAID
raid6check <raid6 device> <start stripe> <number of stripes>
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".
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.
"raid6check" uses directly the component drives as found in /dev. Furthermore, the sysfs interface is needed in order to find out the RAID6 parameters.
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
https://www.kernel.org/pub/linux/utils/raid/mdadm/
Related man pages:
mdadm(8) mdmon(8), mdadm.conf(5), md(4).