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Forum Discussion
RAID6 resync after drive failure: Data Degraded message
I have a ReadyNAS 528 that is set up for RAID6 using X-RAID, purchased in 2018. Someone else set up the system but they moved on, so I have been maintaining it for the past several years. I had 8 dri...
The “Degraded” status makes sense if the failed drive was simply removed and hasn’t been replaced yet. On a redundant ReadyNAS volume, removing a drive leaves the array degraded until a replacement drive is added and the resync completes. Balance, Scrub, and Defrag aren’t substitutes for rebuilding the missing RAID member. I’d check the volume status and logs first, then replace the failed drive with a suitable disk and let the RAID resync. I’d also make sure there’s a current backup before doing anything further.
That’s a good point. I’d avoid running maintenance tasks until the RAID state is clear. I’ve seen similar situations where the difficult part is deciding whether to replace the drive immediately, keep the array degraded for a while, or focus on getting the backup completed first. When there are several options with different risks, I usually write down the choices before acting. For example, if I’m stuck between two possible next steps, I might use a simple yes-or-no tool like decidal just to make the decision process clearer. It doesn’t replace checking the logs or following the ReadyNAS guidance, but it can help separate the decision from the technical troubleshooting. Once the replacement is installed, I’d monitor the resync closely and verify that the volume returns to a healthy state.
Prior to replacing or adding a drive you should ALWAYS first insure the backup is up to date. The RAID re-sync leaves the volume vulnerable to any secondary issue such as drive failure or anything that might be caused by a power outage too long for your UPS to handle. Drive failure is more likely during the re-sync because it puts more stress on the drives than normal usage. Drive failure on another drive is also more likely if they are the same age as one that already failed.
Balance won't do anything here, but also is pretty benign. The MDADM RAID and BTRFS are unaware of each other for a balance, so a degraded state doesn't matter. Still, no sense in doing it.
On an ReadyNAS, scrub starts both a BTRFS scrub and an MDADM re-sync, which should definitely be avoided on a degraded volume. No sense in triggering a re-sync that will not fix the issue but still puts the volume at risk only to have to do yet another re-sync later to actually fix the problem.
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