On Monday August 21, Dexter.Filmore@xxxxxx wrote: > raid5, 4 sata disks, slackware with 2.6.14.6. > Yesterday the machine hung, so I used MagicKey to sync, remount read only and > reboot. > After that the third disk was not assembled into the array. > dmesg came up with: > > [ 34.652268] md: md0 stopped. > [ 34.742673] md: bind<sdb1> > [ 34.742900] md: invalid superblock checksum on sdc1 > [ 34.742920] md: sdc1 has invalid sb, not importing! > [ 34.742941] md: md_import_device returned -22 > [ 34.743257] md: bind<sdd1> > [ 34.743464] md: bind<sda1> > [ 34.743506] raid5: device sda1 operational as raid disk 0 > [ 34.743524] raid5: device sdd1 operational as raid disk 3 > [ 34.743542] raid5: device sdb1 operational as raid disk 1 > [ 34.744128] raid5: allocated 4195kB for md0 > [ 34.744146] raid5: raid level 5 set md0 active with 3 out of 4 devices, alg > orithm 2 > [ 34.744173] RAID5 conf printout: > [ 34.744187] --- rd:4 wd:3 fd:1 > [ 34.744202] disk 0, o:1, dev:sda1 > [ 34.744216] disk 1, o:1, dev:sdb1 > [ 34.744231] disk 3, o:1, dev:sdd1 > > So after throwing a minor fit (my first degraded array) I started > investigating options. Whe I was sure the disk was alright I re-added it and > resyncing started. > It's currently still at it. > > Question: what happened to that superblock? just because it didn't shut down > properly? Disk seems to be ok. The output of mdadm -E /dev/sdc1 might have been interesting, but I guess it is too late for that now. Apart from hardware errors, an incorrect checksum should only happen if some but not all of the superblock is written (it is 8 sectors long). I suspect that is extremely unlikely to happen, and given the symptoms you describe, I think it is extremely unlike to have happened in your case. So I'm afraid I don't know what happened, and unless it happens again, it would be very hard to trace the problem down. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
