In a message dated 1/22/2004 7:42:48 PM Eastern Standard Time, neilb@cse.unsw.edu.au writes: > > My questions are: > > How do I fix this problem? Check that sdh1 is ok (do a simple read check) and then mdadm /dev/md6 -a /dev/sdh1 Neil, Thanks for taking the time to answer my previous email. Please excuse my follow up question. How do I do a "simple read check" on a partition/drive that's been removed from an array but that doesn't have it's own file system on it? Assuming the "failed removed" drive tests out okay on a read check, I understand that you're suggesting I add the drive back to my array. But why isn't it appropriate to Assemble the array with the "force" option? Is it NOT appropriate to use this option once a drive/partition has been marked as "failed and removed"? If not, when is "force" appropriate? Wish there was some more info about these options (like "run" as well). The manual pages give very brief explanations without examples of where they are appropriate. I know it's not your job to educate the whole world. Is this information in any book that one could buy? Is it in the Derek ??? book? Exhaustive google searches (and searches through the Linux Raid archives) have given me clues here and there. But no hard and fast rules of thumb from the person who should know best about mdadm! That said, I -- and others -- certainly appreciate all you contribute to Linux! Regards, Andy Liebman ----------------------------------------------------------------------------- FOR REFERENCE, HERE'S YOUR REPLY TO ME: > I have just encountered a very disturbing RAID problem. I hope somebody > understands what happened and can tell me how to fix it. It doesn't look very serious. > > I have two RAID 5 arrays on my Linux machine -- md4 and md6.. Each array > consists of 5 firewire (1394a) drives -- one partition on each drive, 10 drives in > total. Because the device ID's on these drives can change, I always use MDADM > to create and manage my arrays based on UUIDs. I am using MDADM 1.3. Mandrake > 9.2 with mandrake's 2.4.22-21 kernel. > > After running these arrays successfully for two months -- rebooting my file > server every day -- one of my arrays came up in a degraded mode. It looks as if > the Linux RAID subsystem "thinks" one of my drives belongs to both arrays. > > As you can see below, when I run mdadm -E on each of my ten firewire drives, > mdadm is telling me that for each of the drives in the md4 array (UUID group > 62d8b91d:a2368783:6a78ca50:5793492f ) there are 5 Raid devices and 6 total > devices with one failed. However this array always only had 5 > devices. The "total" and "failed" device counts are (unfortuantely) not very reliable. > > On the other hand, for most of the drives in the md6 arary (UUID group > 57f26496:25520b96:41757b62:f83fcb7b), mdadm is telling me that there are 5 raid > devices and 5 total devices with one failed. > > However, when I run mdadm -E on the drive currently identified as /dev/sdh1 > -- which also belongs to md6 or the UUID group > 57f26496:25520b96:41757b62:f83fcb7b -- mdadm tells me that sdh1 is part of an array with 6 total devices, 5 > raid devices, one failed. > > /dev/sdh1 is identified as device number 3 in the RAID with the UUID > 57f26496:25520b96:41757b62:f83fcb7b. Howver, when I run mdadm -E on the other 4 > drives that belong to md6, mdadm tells me that device number 3 is > faulty. So presumably md thought that sdh1 failed un some way and removed it from the array. It updated the superblock on the remaining devices to say that sdh1 had failed, but it didn't update the superblock on sdh1, because it had failed, and writing to the superblock would be pointless. > > My questions are: > > How do I fix this problem? Check that sdh1 is ok (do a simple read check) and then mdadm /dev/md6 -a /dev/sdh1 > Why did it occur? Look in your kernel logs to find out when and why sdh1 was removed from the array. > How can I prevent it from occurring again? You cannot. Drives fail occasionally. That is why we have raid. Or maybe a better answer is: Monitor your RAID arrays and correct problems when they occur. BY THE WAY, I WAS MONITORING MY ARRAYS -- WHICH IS WHY I PICKED UP THE PROBLEM JUST AFTER IT OCCURRED. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
