False alarm?

I booted up Mac this morning and immediately had a warning from SoftRAID that one of the disks in a mirrored pair had failed and needed to be replaced; the secondary disk had been redesignated as the primary disk pending replacement. I ordered a new disk from Amazon but was not entirely convinced, and so I restarted Mac. This time SoftRAID said that the same disk had a synchronisation problem and could still be used while it was being rebuilt. A minute later and it was done and SR reported that everything was hunky dory with no errors. So I cancelled the order for a new disk. Not sure whether this episode should decrease my confidence in the disk or in SoftRAID, but one or the other (or both) had a bad moment there.

The relevant part of the log:
May 31 08:24:15 - SoftRAID Driver: SoftRAID driver loaded, version 5.5.
May 31 08:24:49 - SoftRAID Driver: The primary disk for the mirror volume "TB-4" () failed. The SoftRAID driver has selected a new primary disk for this volume.
May 31 09:05:54 - SoftRAID Driver: SoftRAID driver loaded, version 5.5.
May 31 09:06:03 - SoftRAID Monitor: SoftRAID Lite Monitor loaded, version 5.5.
May 31 09:06:09 - SoftRAID Monitor: Starting SMART test on all disks which support SMART.
May 31 09:06:10 - SoftRAID Driver: The mirror volume "TB-4" (disk5) is out of sync. A rebuild has started automatically.
May 31 09:06:22 - SoftRAID Monitor: Finished SMART test. No disks failed the SMART test.
May 31 09:07:03 - SoftRAID Driver: The mirror volume "TB-4" (disk5) has been rebuilt successfully.