RAID1 fail did not work properly with SSDs

["Cal Leeming [Simplicity Media Ltd]" <cal.leeming@xxxxxxxxxxxxxxxxxxxxxxxx>]

Hi all,

My apologies if this is the wrong mailing list for this issue, but I
figured my email would be lost in volume if I sent to 'linux-kernel'.

In short, I had 2 SSDs in RAID 1, allocated as a single physical
volume, which had a LVM logical volume mounted as the root partition.

Six months later, one of the SSDs dies, and causes all of hell to break lose:

[27087.234675] sd 0:0:0:0: [sda] Unhandled error code
[27087.234686] sd 0:0:0:0: [sda] Result: hostbyte=DID_BAD_TARGET
driverbyte=DRIVER_OK
[27087.234688] sd 0:0:0:0: [sda] CDB: Read(10): 28 00 00 68 53 88 00 00 08 00
[27087.234693] end_request: I/O error, dev sda, sector 6837128
^^ repeated over 9000 times

Instead of the disk being marked as failed and removed, the root
partition was instead remounted as read-only, mdadm showed no
problems, and required a reboot.

Upon rebooting, RAID still hadn't marked the dying disk as failed or
removed, and began to re-sync!

 root@vicky [/var/log] > cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md0 : active (auto-read-only) raid1 sdb1[0] sdc1[1]
      78122967 blocks super 1.2 [2/2] [UU]

On top of this, even though it was read-only, it kept giving this
error for everything:

 root@vicky [/var/log] > shutdown
bash: /sbin/shutdown: Input/output error

I'm not sure if what I'm seeing here is normal, but thought I should
at least try and ask - I can provide lots more info if needed (got a
huge text file and several screenshots).

Any feedback would be very much appreciated.

Cal Leeming
Simplicity Media Ltd

----------------------------

Here is the short smartctl dump of the disk:

 root@vicky [/home/foxx] > smartctl -a /dev/sda
smartctl 5.40 2010-07-12 r3124 [x86_64-unknown-linux-gnu] (local build)
Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===
Device Model:     M4-CT128M4SSD2
Serial Number:    00000000111603061D7B
Firmware Version: 0001
User Capacity:    128,035,676,160 bytes
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   8
ATA Standard is:  ATA-8-ACS revision 6
Local Time is:    Tue Jan  3 13:54:46 2012 GMT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
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