Thanks. Downloading the logs and digging around led me (eventually) to test.log, which has this entry;

/dev/sda:

Model=WDC WD1003FBYX-01Y7B0 , FwRev=01.01V01, SerialNo= WD-WCAW31075556
Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=50
BuffType=unknown, BuffSize=0kB, MaxMultSect=16, MultSect=?16?
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=268435455
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=yes: unknown setting WriteCache=enabled
Drive conforms to: Unspecified: ATA/ATAPI-1 ATA/ATAPI-2 ATA/ATAPI-3 ATA/ATAPI-4 ATA/ATAPI-5 ATA/ATAPI-6 ATA/ATAPI-7

* signifies the current active mode

This gives me a serial number, which allows me to track the device down to Unit S000, so I'm getting somewhere.

When I come to replace this drive, as it's in a S/W RAID, is it just a matter of pulling and replacing the drive and letting the RAID rebuild, or do I need to do anything else beforehand?