Best option with 3ware 3DM2 when drive has bad sectors

Pretty strange (to say the least).

It sounds like someone (or something) has cause your RAID volume to split. If anyone else has admin authority over this device, I'd ask them if they might have inadvertently reconfigured the volume (maybe they thought they were looking when in fact they were changing). In any event, your primary RAID volume is in degraded mode because it no longer has a hot-spare.

I'd first make absolutely certain I have a 100% good backup (preferably a bare metal backup). The try to re-add the spare to primary RAID volume (the 3.87 TB) volume. You will probably have to delete the goofey new volume before the 3Ware controller will allow this operation.

WARNING: 3.87 TB is big and it will likely take you several days to recover from tape if you need to rebuild your primary RAID volume. If you can wait until Friday @ 5pm (assuming you're organization is not 24x7) and do the work, that would be the best choice. This way if you are forced to recover from backups, you'll have the weekend.

Jim C. http://www.kleobackup.net

I believe you are out of luck. This is one of the dangers of RAID5. Since the array was in use, all the other disks are now out of sync with the original port 10 disk.

updated: Regarding the update read-only mounting...Whether or not this works is really going to be an implementation detail of the 3ware. Even if you mounted read-only, the raid controller could have updated some metadata on the disks and decided this configuration is not recoverable. That's what I would expect.