Mailinglist Archive: opensuse (2576 mails)

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Re: [opensuse] Curious about different software raid signatures in top (md & dm raid)
  • From: Manfred Hollstein <manfred@xxxxxxxxxxxxxxxxx>
  • Date: Tue, 24 Feb 2009 10:06:02 +0100
  • Message-id: <20090224090602.GA6858@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Hi David,

On Mon, 16 Feb 2009, 06:29:55 +0100, David C. Rankin wrote:
[...]
root@zion:/home/david # mdadm -Q -D /dev/md1
/dev/md1:
Version : 01.00.03
Creation Time : Sun Jun 22 01:40:26 2008
Raid Level : raid1
Array Size : 467411004 (445.76 GiB 478.63 GB)
Used Dev Size : 934822008 (891.52 GiB 957.26 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent

Intent Bitmap : Internal
^^^^^^^^^^^^^^^^^^^^^^^^
Update Time : Sun Feb 15 23:27:24 2009
State : active
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

Name : 1
UUID : b119e184:e3bd8652:792c1ed2:3107e924
Events : 12

Number Major Minor RaidDevice State
0 8 54 0 active sync /dev/sdd6
1 8 38 1 active sync /dev/sdc6


I'll go digest man mdadm a bit more. In the mean time, I there any
benefit to
keeping it or removing it? I figure it is there for a reason, but what to you
see in the real world.

It depends... I once had trouble because one disk repeatedly failed and
got kicked from the mirror; when I checked the disk it appeared OK, so I
re-added it to the mirror which resulted again in a full resync. I
eventually found out that it wasn't the disk, but the cables which
caused connectivity to be flaky. Bitmaps definitely help in keeping
synchronization times to a minimum. In my experience you don't need it
very often in your home environment - assuming you're using high quality
cables ;-) - while it's an absolute must-have e.g. in a cluster
environment where you must fail-over the mirror from time to time and
have to live with asynchronous drops between the storage elements.

FWIW, I have bitmaps enabled on all my systems.

HTH, cheers.

l8er
manfred
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