I have a storage pool with 2x2 drives in it. This is an "upgraded" Storage Pool being hosted by Windows 10 1809. One of the drives has started throwing errors -- SMART shows over a thousand recently-logged read errors, and Windows has thrown about a hundred disk events into the log over the past week. For some reason, Storage Spaces insists that the drive is still healthy, but my gut feeling is that it should be replaced. But, I haven't been able to find any solid documentation on how.
With an old-fashioned RAID-1 array, I'd just pull the bad disk, put a new disk in of at least the same size, and then tell it to rebuild the mirror using the new disk. After both drives get replaced with ones of a larger capacity, most systems will then typically let me extend the volume to the size shared by the two drives. But I haven't been able to find any explicit documentation whatsoever of how Storage Spaces handles this situation, whether it is the same or different.
One of the things I've read is that if Storage Spaces detects any sort of error in a Storage Pool, it actually makes the entire Storage Pool permanently read-only. This sounds pretty wacky to me, but I thought I'd mention it in case someone reading this can confirm or deny.
The best I've been able to put together from the bits and pieces I've found is that what I'm supposed to do is:
- Install two new disks.
- Add these disks in tandem to the Storage Pool as mirrored elements.
- Tell the Storage Pool that I want to "retire" the mirror pair that contains the bad drive.
- Wait for Storage Pool to evict all the data from those drives by moving it into the blank space in the new drives.
- Tell Storage Pool that I don't want the mirror set of old drives to be in the pool any more.
Is this correct? What happens if one of the drives in one of those mirrored pairs goes missing? Does the Storage Pool continue to read/write data from that drive's counterpart, just like a degraded RAID-1 array? And, is there a more direct way to say, "Yeah, just rebuild that particular pair with this new drive"?
I've seen screenshots of the step 3 I described above, with a link button "Prepare for removal" to the right of each of the physical disks, but when I navigate to that same screen on my system, that link doesn't appear for me. Does it only appear when there is enough space elsewhere in the storage pool for it to be possible to relocate the data? Is there something you have to do to make it appear? Does it only appear for certain configurations?
I am surprised that I haven't been able to find any clear information walking through this scenario of wanting to replace a failing drive that's part of a mirror set. In my prior experience it is a fairly common occurrence.