On Tue, Aug 17, 1999 at 04:18:27AM -0600, Ziber wrote:
> Hello,
> I am is facing problem in Raid.
> I have created Raid1 on 500Mb partitions on sda5 and sdb5. For testing purpose
> i disconnect power
>
> from sdb while copying data to the Raid. But the raid is still trying to
> access sdb and then
>
> giving errors and do it in an infinite loop.
It's a problem with your SCSI driver or hardware. It's not directly related to
RAID, except for the fact that the RAID layer suffers from the shortcomings in
those lower layers...
After a boot (still with the power disconnected) your RAID should run just
fine, but in degraded mode of course.
The AIC7xxx and NCR8xx drivers should handle failing devices fairly well, but
there could still be problems... Your mail indicates that someone should probably
take a looksee on the AIC7xxx error handling.
Sometimes you will see that the entire SCSI bus locks up, so your entire RAID
dies when one disk dies. This is unfortunate, but we're limited by the hardware
or - at best - the SCSI drivers here.
I've personally never seen a disk hang the bus, except when I did nasty stuff
like you tried. Usually a disk gives a hard read/write error, the RAID layer
detects the error, and handles the situation just fine.
If you have electrical failures on the bus, or if your SCSI drivers fail, there's
little the RAID code can do about this.
If you're really paranoid, you can put each disk on it's own SCSI channel to
minimize the chance of one disk taking down the others with it.
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