status: inactive - array degraded - disk sync failure

Thanks for the help.

Situation now resolved and am posting what worked for me in case useful for anyone else.

The key was to schedule the volume scan check or something similar on restart.
Cant find where I saw it but might have been on the restart interface itself

Anyway after scheduling this check when I booted up the system to start backing data off it I found that fsck/efsck had run and fixed a load of errors on the problem drive
and this had allowed the sync to complete successfully!

So instead of a degraded array with one drive as status: spare
I now had a redundant array with 2 drives showing status: OK !!!!
Great!!!

Am running a backup of key information from the drive anyway as I am sure the problem drive is going to fail on me.
The sooner the better as once it fails completely I can get it replaced by Seagate.
Theoretically I should be entitled to get it replaced now but would have to demonstrate with Seagate tools or similar that the drive was beyond recovery. Simplest to wait until it dies so there is no argument.

So to summarize:
One of 2 drives in my array failed and the remaining drive started to show errors
Adding a new good drive to replace the completely failed drive did not obtain a successful sync and redundant array
the solution for me was to restart systems and schedule a volume scan on restart when requesting restart
this reported fixing loads of errors on the failing drive
and the good drive was able to complete sync with failing drive with its errors fixed



Thanks again for the help.
Hope this is useful to someone else

Regards
Ivor