[ale] motherboard RAID versus software RAID

[Pat Regan]

Christopher Fowler wrote:
> 1.  Sometimes a drive will be dropped from the raid.  Not sure why but
>     sometimes it happens
> 
> 2.  I've had one case where the ext3 filesystem on a RAID1 device 
>     became corrupted and unreadable.  The software raid simply copied
>     this corruption across 2 drives.  I never figured out why and was 
>     never to explain to the customer why I had to totally reinstall FC2
>     even though he had RAID1 with 2 good drives.   Maybe something
>     went stupid in the RAID1 driver that wrote bad data that screwed
>     everything.

Have you had both problems on the same machine?  If so, are you
absolutely sure both drives are good?  If one drive silently reads bata
data it is very possible that it could be rewritten to the other drive
at some other point (during a rebuild, or while an application is
actually working with the data).

Non-SCSI drives are much more likely to not report a read error, unless
it is a very bad error.  IDE/SATA drives only remap sectors on writes, I
believe.

Also, RAID 1 is SUPPOSED to copy corruption from one drive to the other.
 It has no understanding of filesystems and data, it is very
unintelligent and just makes sure both drives have the same data.

Pat
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