I recently got an IO Error on one of my RAID5 members; on a 3 disk fakeRAID array. I didn't notice at the time - there was only a message in /var/log/kern.log - so I had continued running the machine from that partition for a good while longer.

The BIOS / Intel RAID Manager didn't pick up any problems, but when I chose to boot from that partition, / was being mounted read-only.

Now I'm booted from a recovery partition, and have just run e2fsck -c -y on the partition, which has picked up quite a few errors, including: "Multiply-claimed blocks", "Unattached inode", "Free inodes count wrong for group #xxx", etc.. It has also reproduced the IO error in kern.log, so dmraid has degraded the array and I can now tell easily which drive has failed.

Now, what to do about the dodgy drive? I will get an advance RMA, but that takes about 5 days, so in the mean-time, I need a running machine, and a degraded RAID5 volume is not good karma!

The messages I'm seeing from dmesg are:-

ata3.00: exception Emask 0x10 SAct 0x1 SErr 0x280100 action 0x6 frozen
ata3.00: irq_stat 0x08000000, interface fatal error
ata3: SError: { UnrecovData 10B8B BadCRC }
ata3.00: failed command: READ FPDMA QUEUED
ata3.00: cmd 60/00:00:00:0b:0c/01:00:14:00:00/40 tag 0 ncq 131072 in
         res 40/00:04:00:0b:0c/00:00:14:00:00/40 Emask 0x10 (ATA bus error)
ata3.00: status: { DRDY }
ata3: hard resetting link
ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata3.00: configured for UDMA/133
sd 2:0:0:0: [sdb]
Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
sd 2:0:0:0: [sdb]
Sense Key : Aborted Command [current] [descriptor]
Descriptor sense data with sense descriptors (in hex):
        72 0b 00 00 00 00 00 0c 00 0a 80 00 00 00 00 00
        14 0c 0b 00
sd 2:0:0:0: [sdb]
Add. Sense: No additional sense information
sd 2:0:0:0: [sdb] CDB:
Read(10): 28 00 14 0c 0b 00 00 01 00 00
end_request: I/O error, dev sdb, sector 336333568
ata3: EH complete
device-mapper: dm-raid45: CRITICAL: io error on device /dev/sdb in region=336329728; DEGRADING RAID set
device-mapper: dm-raid45: further device error messages suppressed

Am I right in thinking that (from the above dmesg errors) that only some regions of the drive are bad? If so, can I continue to use the drive whilst avoiding those bad blocks? I'm inclined to format the drive and rebuild the array on to it, until a replacement arrives. Is that a bad idea?

Also, the SMART tests seem to be fine on all RAID disks...

1 Answer 1


I'd just wait for the RMA. If you try to reformat and rebuild the array, you'll be putting extra stress on the two good disks for (probably) no good reason which is risky. If it's a server, leave the disk in there for air flow until the new disk arrives.

  • Fair point. I've recovered my current projects from the partitions, which is good. Currently running from an Ubuntu recovery partition, which I try not to use too vigorously, as it's a 2TB, relatively budget drive, with a separate, big storage partition on it (and no backup!). It might be a few weeks before I get and install the RMA, unfortunately, for reasons not worth going in to here. I am going to add an update to my question, though...
    – Alex Leach
    Commented Dec 12, 2012 at 18:18

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