[Durham] SMART errors

[Oliver Burnett-Hall]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Does anyone know much about SMART?

I've got my backups going to a system which is running a three-disk
RAID5 array. For the last few days I've been receiving warnings from
smartd about problems with one of the disks and from mdadm about a
degraded array. I'm a bit clueless about all of this and Google hasn't
given my any idiot-friendly primers for what's happening.

First off, the SMART errors. I'm getting these two messages from smartd
repeated in syslog every half hour:
    Device: /dev/sdb [SAT], 14 Currently unreadable (pending) sectors
    Device: /dev/sdb [SAT], 14 Offline uncorrectable sectors

That seems a fairly clear: /dev/sdb is failing. However when I run any
self-tests (both short and long) the drive passes them. Surely that
can't be right?

The messages from mdadm are even less helpful. It says:
    A DegradedArray event had been detected on md device /dev/md0.
    Faithfully yours, etc.
    P.S. The /proc/mdstat file currently contains the following:
    Personalities : [raid1]
    md0 : active raid1 sdc1[1]
        1953279872 blocks super 1.2 [2/1] [_U]
    unused devices: <none>

That is confusing me. I set up a RAID5 array across sdb, sdc and sdd
but now it's talking about a RAID1 only on sdc. If sdb has died should
it not still being showing a degraded RAID5 on sdc and sdd

The drive is still well within its warranty period so there's the
obvious solution of getting a replacement drive off WD, but I'm curious
to understand what's happening here.

- - olly

-----BEGIN PGP SIGNATURE-----

iQJLBAEBCAA1LhxPbGl2ZXIgQnVybmV0dC1IYWxsIDxvbGx5QGJ1cm5ldHQtaGFs
bC5jby51az4FAlRfiToACgkQBnjjQqyac0jgeA/7BCpvrZPEzqxxn9kH16iIAEoW
GIo50NiyjEsB+T+T5jLmyIX+5zXAb6xU/jCxeuitJ+W5HGMqtrHfrHt0RpbzJv+k
sMLV4BaN+7VFmS0PGkKj09IDCdiLYfv5m0ohuJctQQgVDICDw6rEG739N+x5QtWn
n15LvwfpbfbuIIjlLOVkkOZst80WnZwBp+xZ2qG1tbugHj/vsY88Qo6XInCpBvMz
wWyTvicmNKJn/sToeRArSPS8ozZ4z0IhnDswCus1U8XJOiq1qgtUcFZyWjokHEzs
QWuBV+i6OtK0J2neDkhkUBOM/AlLTSqZwDNgF72Tfz7m7S+vYesu/UIxG4xWQ0oe
+VccfxeBe4fgRsuaxykO5VYAGdJTFazfvi+mETENaJm3K+MRDcQsblOj2bgMr8ul
7xLCaxDMd6CjGtj6faak3z7WZVo3WOs6q1ahRUeMHdAIX4ThPielEDCzXMZiI6YA
fuZjg9dwoR//ci74gEYdZ8QSduo1UE/mlm067xOtTgaUfN4X0KOG3sPNkwg/dNbn
gu/qac+qcZ5iKizTDYTmgv+2hiWQTpFsC05KDhIIbzOt86KJIgblKbSnMNC4XpcC
AensQB9IVZzWGOzUAx1iaasL22o5tsz9APBbKxusMad9rD3+SleRRWlg0oasUfg8
R9/oU594GzBxMTwWg4w=
=Kbve
-----END PGP SIGNATURE-----