[CentOS] more software raid questions

fred smith fredex at fcshome.stoneham.ma.us
Tue Oct 19 19:59:59 EDT 2010


hi all!

back in Aug several of you assisted me in solving a problem where one
of my drives had dropped out of (or been kicked out of) the raid1 array.

something vaguely similar appears to have happened just a few mins ago,
upon rebooting after a small update. I received four emails like this,
one for /dev/md0, one for /dev/md1, one for /dev/md125 and one for
/dev/md126:

	Subject: DegradedArray event on /dev/md125:fcshome.stoneham.ma.us
	X-Spambayes-Classification: unsure; 0.24
	Status: RO
	Content-Length: 564
	Lines: 23

	This is an automatically generated mail message from mdadm
	running on fcshome.stoneham.ma.us

	A DegradedArray event had been detected on md device /dev/md125.

	Faithfully yours, etc.

	P.S. The /proc/mdstat file currently contains the following:

	Personalities : [raid1] 
	md0 : active raid1 sda1[0]
	      104320 blocks [2/1] [U_]
	      
	md126 : active raid1 sdb1[1]
	      104320 blocks [2/1] [_U]
	      
	md125 : active raid1 sdb2[1]
	      312464128 blocks [2/1] [_U]
	      
	md1 : active raid1 sda2[0]
	      312464128 blocks [2/1] [U_]
	      
	unused devices: <none>

firstly, what the heck are md125 and md126? previously there was
only md0 and md1.... ????

secondly, I'm not sure what it's trying to tell me. it says there was a 
"degradedarray event" but at the bottom it says there are no unused devices.

there are also some messages in /var/log/messages from the time of the
boot earlier today, but they do NOT say anything about "kicking out"
any of the md member devices (as they did in the event back in August):

	Oct 19 18:29:41 fcshome kernel: device-mapper: dm-raid45: initialized v0.2594l
	Oct 19 18:29:41 fcshome kernel: md: Autodetecting RAID arrays.
	Oct 19 18:29:41 fcshome kernel: md: autorun ...
	Oct 19 18:29:41 fcshome kernel: md: considering sdb2 ...
	Oct 19 18:29:41 fcshome kernel: md:  adding sdb2 ...
	Oct 19 18:29:41 fcshome kernel: md: sdb1 has different UUID to sdb2
	Oct 19 18:29:41 fcshome kernel: md: sda2 has same UUID but different superblock 
	to sdb2
	Oct 19 18:29:41 fcshome kernel: md: sda1 has different UUID to sdb2
	Oct 19 18:29:41 fcshome kernel: md: created md125
	Oct 19 18:29:41 fcshome kernel: md: bind<sdb2>
	Oct 19 18:29:41 fcshome kernel: md: running: <sdb2>
	Oct 19 18:29:41 fcshome kernel: raid1: raid set md125 active with 1 out of 2 mir
	rors
	Oct 19 18:29:41 fcshome kernel: md: considering sdb1 ...
	Oct 19 18:29:41 fcshome kernel: md:  adding sdb1 ...
	Oct 19 18:29:41 fcshome kernel: md: sda2 has different UUID to sdb1
	Oct 19 18:29:41 fcshome kernel: md: sda1 has same UUID but different superblock 
	to sdb1
	Oct 19 18:29:41 fcshome kernel: md: created md126
	Oct 19 18:29:41 fcshome kernel: md: bind<sdb1>
	Oct 19 18:29:41 fcshome kernel: md: running: <sdb1>
	Oct 19 18:29:41 fcshome kernel: raid1: raid set md126 active with 1 out of 2 mirrors
	Oct 19 18:29:41 fcshome kernel: md: considering sda2 ...
	Oct 19 18:29:41 fcshome kernel: md:  adding sda2 ...
	Oct 19 18:29:41 fcshome kernel: md: sda1 has different UUID to sda2
	Oct 19 18:29:41 fcshome kernel: md: created md1
	Oct 19 18:29:41 fcshome kernel: md: bind<sda2>
	Oct 19 18:29:41 fcshome kernel: md: running: <sda2>
	Oct 19 18:29:41 fcshome kernel: raid1: raid set md1 active with 1 out of 2 mirrors
	Oct 19 18:29:41 fcshome kernel: md: considering sda1 ...
	Oct 19 18:29:41 fcshome kernel: md:  adding sda1 ...
	Oct 19 18:29:41 fcshome kernel: md: created md0
	Oct 19 18:29:41 fcshome kernel: md: bind<sda1>
	Oct 19 18:29:41 fcshome kernel: md: running: <sda1>
	Oct 19 18:29:41 fcshome kernel: raid1: raid set md0 active with 1 out of 2 mirrors
	Oct 19 18:29:41 fcshome kernel: md: ... autorun DONE.

and here's /etc/mdadm.conf:

	# cat /etc/mdadm.conf

	# mdadm.conf written out by anaconda
	DEVICE partitions
	MAILADDR fredex
	ARRAY /dev/md0 level=raid1 num-devices=2 uuid=4eb13e45:b5228982:f03cd503:f935bd69
	ARRAY /dev/md1 level=raid1 num-devices=2 uuid=5c79b138:e36d4286:df9cf6f6:62ae1f12

which doesn't say anything about md125 or md126,... might they be some kind of detritus
or fragments left over from whatever kind of failure caused the array to become degraded?

do ya suppose a boot from power-off might somehow give it a whack upside the head so
it'll reassemble itself according to mdadm.conf?

I'm not sure which devices need to be failed and re-added to make it clean again (which
is all I had to do when I had the aforementioned earlier problem.)

Thanks in advance for any advice!

Fred

-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
                        The Lord is like a strong tower. 
             Those who do what is right can run to him for safety.
--------------------------- Proverbs 18:10 (niv) -----------------------------


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