RAID 10 Failed and One Mirror Pair Is Missing
RAID 10 needs at least one usable, current member from every required mirror pair. If neither side of one pair is available, the controller cannot assemble a complete virtual disk even when the remaining drives appear healthy.
Do not replace several drives, recreate the array, or discard members reported failed. Preserve the complete set and original bay order.
What this condition means
Missing may mean physically unreadable, timed out, disconnected, excluded by metadata, assigned to the wrong position, or no longer accepted by the controller.
The two members may not have failed in the same way. Useful readable regions from either side can matter when reconstructing the stripes assigned to that pair.
What to record
- Controller, member count, stripe size if known, and expected capacity
- Original mirror-pair map if known
- Bay, serial number, size, and status of every member
- Failure order, timeouts, errors, and unusual sounds
- Every replacement, force-online, rebuild, recreation, or repair already attempted
What not to do
- Assume both reported members are physically unreadable
- Replace multiple members and start a rebuild
- Force either member online
- Discard original or replacement drives
- Create a new RAID 10 over the surviving set
How ADR evaluates it
ADR evaluates both members of the missing pair independently and confirms the pair map across the complete array.
Readable regions, generation, and stripe coverage are compared to determine whether a complete or useful partial reconstruction is possible.
What happens next
A missing pair is more serious than failures spread across different pairs, but controller status alone does not determine the outcome. The complete member set must be examined before recovery options are known.