Readynas Duo: Dead drive 1 - what are my options?

Ok. THis is a bit more worrying (or not). Removed drive 1 and reseated, and at some point, rebooted, I suspect. Drive went into sync and now shows as fine...

Here's SMART+ info about the drive 1 (which previously reported as DEAD):
Model: SAMSUNG HD103UJ
Serial: SXXXXXXXXXXXXXXXXXXX
Firmware: 1AA01113

SMART Attribute

Raw Read Error Rate 0
Spin Up Time 10960
Start Stop Count 113
Reallocated Sector Count 0
Seek Error Rate 0
Seek Time Performance 0
Power On Hours 19453
Spin Retry Count 0
Calibration Retry Count 0
Power Cycle Count 113
Read Soft Error Rate 0
Temperature Celsius 35
Hardware ECC Recovered 820452
ALL OTHER ENTRIES ZERO


And, for info, here's drive 2 (never reported as DEAD)
SMART Attribute

Raw Read Error Rate 0
Spin Up Time 10480
Start Stop Count 114
Reallocated Sector Count 0
Seek Error Rate 0
Seek Time Performance 0
Power On Hours 19588
Spin Retry Count 0
Calibration Retry Count 0
Power Cycle Count 114
Read Soft Error Rate 0
Temperature Celsius 35
Hardware ECC Recovered 38346394
ALL OTHER ENTRIES ZERO


Any thoughts on any of this? What would other people do in my position? (apart from make sure backup is reliable)