After more than four years (24/7) of serving my storage needs in my DiskStation, two of my five disks are showing symptoms of being worn out. They started showing bad blocks and therefore became a risk to my precious data. The unit was still working OK and as long as that is the situation I should be able to replace them without data loss. I purchased two new NAS disks and started to replace the disks one by one. (It’s obvious that you have to create a backup of your data on another target than your DiskStation. RAID is not a backup.) You can not replace more disks at once as you have configured the amount of disks for redundancy purposes. Even if you have configured two disks for redundancy, it’s a good idea to replace the disks one by one: it protects your data during the repair of the stripe set.
It’s a little bit tricky to decide witch disk is being replaced first. I decided to start with the one that has the most bad blocks. (Crossing my fingers that not the other one decides to fail during the repair process…) I didn’t dare to replace the disk while the unit was running, so I brought it down and replaced the first disk. After the reboot the DiskStation started complaining (obvious) about a degraded RAID. It has to be repaired.
As you will find all over the internet, those repair actions can take hours or even days. As long as the repair isn’t finished, the data is vulnerable to disk failures. Even in a stripe set. So this situation has to exist as short as possible. After some digging in several forums I found a clue that helps to decrease the repair time of a stripe set:
Turn off file indexing on all shared folders.
It turns out that this increases the speed of repairing dramatically. The exact time of the repair is hard to predict. It depends on the hardware of the DiskStation, the size of the disk and the services running during the repair.
An other good idea is to stop all packages and services that are not really needed and can be missed for a couple of hours. Depending of the amount of disk interaction each package or services has, it can contribute to increase the repair speed when it’s not writing to disk. Candidates might be SymForm (or others), DownloadStation, CloudSync, PhotoStation, MediaServer and VideoStation. Don’t forget to turn them on again when as the repair is done.