This guide can serve as a general to do list when you receive a disk error on a NAS device protected by redundant disks, for example: RAID 1, RAID 4, RAID 5, etc. With this process, you will not have any data loss, unless you unplug the wrong disk or perform the steps indicated here not in the correct order. So, please pay attention to the instructions.
First of all it’s important to identify the correct disk to replace, and keep in mind that, for data loss risks, you do not want to run a failing disk for long. A failing disk is a disk on which, bad sectors are starting to appear, and the SMART disk troubleshooting indicates an imminent failure.
To identify the correct disk to replace, use the software provided by NAS, or, you might have individual lights indicating each disk status on the actual device. So refer to the NAS manual to help in identify where the disk is located in the device.
Once you have identified the disk, you need to order a disk of the exact size or bigger, smaller disks cannot be used to replace a failed disk in a raid configuration. Ideally, to maintain the same performance, you would buy the exact same disk, but if you cannot find it, buy a disk with the same or bigger size, but a type compatible with your NAS.
Once you have the new disk in hand, follow the steps:
- Power off the NAS Device and unplug the device
- Open the case to access the disk array
- Remove the failing/failed disk
- Insert the new disk in the empty slot
- Close the case
- Plug the NAS device and Power it back on
Once the device is booted, it should start the rebuilding process automatically, but you might want to check the NAS console, normally via browser to see the status. Some NAS do require a manual initiation of the rebuild.
Be careful, the rebuild can take a long time, and depending on how big the volume is, it might take a day or two to rebuild.
That’s it, you have replaced a failing disk in a NAS running redundancy.