A little story of failed raid5 (3ware 8000 series)

[Martin Nilsson]

Artem Kuchin wrote:
> But i don't understand how and why it happened. ONly 6 hours ago (a 
> night before)
> all those files were backed up fine w/o any read error. And now, right 
> after replacing
> the driver and starting rebuild it said that there are bad sectors all 
> over those file.
> How come?

That is what patrol read is intended to detect before it is a problem. 
In a RAID5 array the checksums are only used when reconstructing data, 
if you have a bad block in a checksum sector it will not be detected 
until a drive have failed and you try to rebuild the array, 
unfortunately at that time it is too late...

Beware that OS software solutions like diskcheckd will not find this as 
it only reads the data, not the checksums, it must be done on the 
controller.

Regards,
Martin