Matthew Wild <M.Wild@rl.ac.uk> writes:
>Anton Ertl wrote:
>> Matthew Wild <M.Wild@rl.ac.uk> writes:
>>> Personally, I've generally preferred hardware RAID. I've had software
>>> RAID systems not notice a drive failing,
>>
>> Which software RAID was that?
>>
>Standard Linux md RAID.
>
>>> causing corruption of the
>>> filesystem.
>>
>> How does not noticing a failing drive cause the corruption of the file
>> system?
>>
>Because as one drive is failing it is corrupting any accesses to that disk.
....
>I was just pointing out that while a disk is failing, the software RAID
>has not noticed and limped along still trying to use the failing disk
>which happily provides garbage when accessed.

It's an unusual failure mode if a drive delivers wrong data without
reporting an error. Why do you believe that the hardware RAID would
have fared better when confronted with such a drive?

>In my experience, the
>hardware RAID systems I have used, 3Ware, Digital/Compaq/HP RA8000,
>MA8000, MSA1500 (quite horrible to administer), manage their arrays
>fairly conservatively and drop disks pretty quickly.

In my experience md is overly conservative and drops drives pretty
quickly: We had a box that now and then reported IDE errors that the
kernel could recover from by doing an IDE reset; however, by then md
had assumed that the drive had failed and had dropped it from the
array, so we needed to re-add it to the array manually, which was
pretty annoying. OTOH, maybe this annoyance was good, because we
eventually fixed the problem.

- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html