[CentOS] Software RAID1 with CentOS-6.2

[Luke S. Crawford]

On Wed, Feb 29, 2012 at 11:27:53AM +1100, Kahlil Hodgson wrote:
> Now I start to get I/O errors on printed on the console.  Run 'mdadm -D
> /dev/md1' and see the array is degraded and /dev/sdb2 has been marked as
> faulty.

what I/O errors?


> So I start again and repeat the install process very carefully.  This time I
> check the raid array straight after boot.
> 
>     mdadm -D /dev/md0   -   all is fine.
>     mdadm -D /dev/md1   -   the two drives are resyncing.
> 
> 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.  At this rate
> its going to take a whole day to do a single minimal install and I'm sure I
> would have heard others complaining about the process.

Yeah, it's normal for a raid1 to 'sync' when you first create it.
the odd part is the I/O errors. 

> Any ideas what is going on here? If its bad drives, I really need some
> confirmation independent of the software raid failing. I thought SMART or
> badblocks give me that. Perhaps it has nothing to do with the drives.  Could a
> problem with the mainboard or the memory cause this issue?  Is it a SATA3
> issue?  Should I try it on the 3Gb/s channels since there's probably little
> speed difference with non-SSDs? 

look up the drive errors.   

Oh, and my experience?  both wd and seagate won't complain if you
error on the side of 'when in doubt, return the drive'  - that's what I
do.   

But yeah, usually smart will report something... at least a high reallocated
sectors or something.