[CentOS] Software RAID1 with CentOS-6.2

Wed Feb 29 00:43:10 UTC 2012
Keith Keller <kkeller at wombat.san-francisco.ca.us>

On 2012-02-29, Kahlil Hodgson <kahlil.hodgson at dealmax.com.au> wrote:
> 2. Reasonably good PC hardware (i.e. not budget, but not server grade either)
> with a pair of 1TB Western Digital SATA3 Drives.

One thing you can try is to download WD's drive tester and throw it at
your drives.  It seems unlikely to find anything, but you never know.
The tester is available on the UBCD bootable CD image (which has lots of
other handy tools).

Which model drives do you have?  I've found a lot of variability between
WDxxEARS vs their RE drives.

> Okay, that is odd. The RAID1 array was created at the start of the install
> process, before any software was installed. Surely it should be in sync
> already?  Googled a bit and found a post were someone else had seen same thing
> happen.  The advice was to just wait until the drives sync so the 'blocks
> match exactly' but I'm not really happy with the explanation.

Supposedly, at least with RAID[456], the array is completely usable when
it's resyncing after an initial creation.  In practice, I found that
writing significant amounts of data to that array killed resync
performance, so I just let the resync finish before doing any heavy
lifting on the array.

> Anyway, I leave the system to sync for the rest of the day.  When I get back to
> it I see the same (similar) I/O errors on the console and mdadm shows the RAID
> array is degraded, /dev/sdb2 has been marked as faulty.  This time I notice
> that the I/O errors all refer to /dev/sda.  Have to reboot because the fs is
> now readonly.  When the system comes back up, its trying to resync the drive
> again. Eh?

This sounds a little odd.  You're having IO errors on sda, but sdb2 has
been kicked out of the RAID?  Do you have any other errors in
/var/log/messages that relate to sdb, and/or the errors right around
when the md devices failed?


kkeller-usenet at wombat.san-francisco.ca.us