[CentOS] Re: question about software Raid 1
Kanwar Ranbir Sandhu
m3freak at thesandhufamily.ca
Wed Oct 1 15:11:20 UTC 2008
On Sun, 2008-09-21 at 21:01 +0200, Kay Diederichs wrote:
> Fact is that with CentOS-5 kernels (but not with CentOS-4, as this
> functionality became available in kernel 2.6.17) you could (or rather
> _should_ regularly)
> echo check > /sys/block/mdX/md/sync_action
> to check agreement between the two (or more) copies. When this finishes,
> /sys/block/mdX/md/mismatch_cnt shows you the number of mismatches. You
> can fix these with
> echo repair > /sys/block/mdX/md/sync_action
Interesting. I'll give this a go on my own desktop system which is
running RAID 1.
You said above, "When this finishes...", but how do you know the check
is completed? I saw this in /var/log/messages:
Oct 1 11:02:47 ranbir kernel: md: data-check of RAID array md0
Oct 1 11:02:47 ranbir kernel: md: minimum _guaranteed_ speed: 1000 KB/sec/disk.
Oct 1 11:02:47 ranbir kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for data-check.
Oct 1 11:02:47 ranbir kernel: md: using 128k window, over a total of 104320 blocks.
Oct 1 11:02:48 ranbir kernel: md: md0: data-check done.
Oct 1 11:02:48 ranbir kernel: RAID1 conf printout:
Oct 1 11:02:48 ranbir kernel: --- wd:2 rd:2
Oct 1 11:02:48 ranbir kernel: disk 0, wo:0, o:1, dev:sda1
Oct 1 11:02:48 ranbir kernel: disk 1, wo:0, o:1, dev:sdb1
There was nothing else after the last line. I don't know exactly what
the "disk" lines mean.
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