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1.\" -*- nroff -*-
2.\" Copyright Piergiorgio Sartor and others.
3.\" This program is free software; you can redistribute it and/or modify
4.\" it under the terms of the GNU General Public License as published by
5.\" the Free Software Foundation; either version 2 of the License, or
6.\" (at your option) any later version.
7.\" See file COPYING in distribution for details.
8.TH RAID6CHECK 8 "" v1.0.0
9.SH NAME
10raid6check \- check MD RAID6 device for errors
11.I aka
12Linux Software RAID
13
14.SH SYNOPSIS
15
16.BI raid6check " <raid6 device> <start stripe> <number of stripes>"
17
18.SH DESCRIPTION
19RAID6 devices in which one single component drive has errors can use
20the double parity in order to find out which component drive.
21The "raid6check" tool checks, for each stripe, the double parity
22consistency, reports mismatches and, if possible, which
23component drive has the mismatch.
24Since it works at stripe level, it can report different drives with
25mismatches at different stripes.
26
27"raid6check" requires a non-degraded RAID6 MD device as first
28parameter, a starting stripe (usually 0) and the number of stripes
29to be checked.
30If this third parameter is also 0, it will check the array up to
31the end.
32
33"raid6check" will start printing information about the RAID6, then
34for each stripe, it will report the parity rotation status.
35In case of parity mismatches, "raid6check" reports, if possible,
36which component drive could be responsible. Otherwise it reports
37that it is not possible to find the component drive.
38
39If the given MD device is not a RAID6, "raid6check" will, of
40course, not continue.
41
42If the RAID6 MD device is degraded, "raid6check" will report
43an error and it will not proceed further.
44
45No write operations are performed on the array or the components.
46Furthermore, the checked array can be online and in use during
47the operation of "raid6check".
48
49.SH EXAMPLES
50
51.B " raid6check /dev/md0 0 0"
52.br
53This will check /dev/md0 from start to end.
54
55.B " raid6check /dev/md3 0 1"
56.br
57This will check the first stripe of /dev/md3.
58
59.B " raid6check /dev/md1 1000 0"
60.br
61This will check /dev/md1 from stripe 1000 up to the end.
62
63.B " raid6check /dev/m127 128 256"
64.br
65This will check 256 stripes of /dev/md127 starting from stripe 128.
66
67.B " raid6check /dev/md0 0 0 | grep -i error > md0_err.log"
68.br
69This will check /dev/md0 completely and create a log file only
70with errors, if any.
71
72.SH FILES
73
74"raid6check" uses directly the component drives as found in /dev.
75Furthermore, the sysfs interface is needed in order to find out
76the RAID6 parameters.
77
78.SH BUGS
79Negative parameters can lead to unexpected results.
80
81It is not clear what will happen if the RAID6 MD device gets
82degraded during the check.
83
84.PP
85The latest version of
86.I raid6check
87should always be available from
88.IP
89.B http://www.kernel.org/pub/linux/utils/raid/mdadm/
90.PP
91Related man pages:
92.PP
93.IR mdadm (8)
94.IR mdmon (8),
95.IR mdadm.conf (5),
96.IR md (4).