RAID 5 failure

[dward]

Intel Mac Pro with Snow Leopard, 4 internal 2tb drives configured as a RAID 5 using the Apple RAID card. One of the four disks, always the same one (#4) occasionally drops out of the RAID and becomes a roaming disk instead of a spare. I get an error message from RAID utility telling me the array has failed, and when I look in the utility, the naughty disk isn't visible. Only disks 1 through 3. If I restart the machine the 4th disk appears but is listed as roaming. I can use the pull down menu to "Make Spare", thus reassigning disk 4 to the RAID set. It takes several days to re-establish itself as part of the RAID.

But then a few days later the same disk drops out of the RAID again. Is this a hardware problem with the RAID card? Or is there a software fix for this behavior?


thanks,
David Ward

 

[doktor gummi]

While I haven't seen this behaviour on Apple kit, I have seen it pretty much everywhere else. It's the drive; most likely if you took it out and ran it in a different machine it would never ever fail again. This "in/out" behaviour dates back to the days of SCSi RAID5's in HP rackmounts. Generally in modern machines with SATA drives, the failure modes are much more low level and painful - beachball mode forever, in one case of a dead drive on a Sonnet card. Unplug the SATA cable and the rest of the server sped right up...

In your case, my rather random suggestion is that the drives as a set are a bit high on the power draw, or that the one you're seeing drop out is higher than the rest. This is very hard to verify inside a Mac Pro!