We've got an Open-E DSS Lite box (v6 v5845) with 4TB expansion license running a S/W RAID5 on 4 x 1TB WD RE SATA disks. This has been running fine, and all SMART settings for the disks show PASSED. Over the weekend I started getting errors from this NAS as follows;

2012/06/06 20:07:31 smartd: Device: /dev/sda, 2 Currently unreadable (pending) sectors

So, while the SMART status in the GUI shows ok, there are problems. This doesn't actually tell me which disk has the problem either, so what's the best way of finding this out? Is it worth running a filesystem repair from the C-A-X console?

Any advice appreciated.