I watched Will’s COMPLETE BEGINNER’S GUIDE for Synology NAS - 2023 DSM 7.2 and setup my Synology 1522+ to those settings. I installed 3-20tb Ironwolf drives choosing SHR Raid. After downloading & installing several synology programs, I let it run for several days to finish the data scrubbing. Then I tried to set one of the drives as a hot spare. But the option is not available. So I tried to remove the drive from the pool, but it complained that I had to uninstall the programs and I had immutable snapshots. I have not put any data on the drive, other than the synology programs, so nothing will be lost. But how do I simply remove one drive from the pool to make it a hot spare?
Philisher, I have a 1522+, home user, I believe when you first started with three drives installed using SHR it will create a one drive failure tolerance RAID-5 configuration, so when you pulled the one drive, SHR flagged your storage space as degraded. You will want to start by designating two drives in SHR as part of your storage pool, it will create a mirrored RAID-1 configuration, which has a one drive failure tolerance. Then designate the third drive as a hot spare for that storage pool. It sounds as if you designated all three drives for your storage pool. With your three 20tb drives in a RAID-1 with a hot spare, you will have about 20tb of storage available. If you keep your current RAID-5, one drive tolerant failure, then you will have about 40tb of storage. Synology Knowledge Center has several articles as to how to configure.
I strongly discourage the use of hot spares when you have regular access to your NAS. There are many reasons… for starters, a hot spare is never idle, so you are reducing the drive’s lifetime while it is in service as a hot spare.
Otherwise, if this is a remote NAS, a hot spare may prove helpful, however it should not be a given, unless circumstances warrant.
Thanks for the heads up on the no idle issue with a hot spare. I guess I will just setup a new separate volume.
I decided to just erase everything and start over from scratch part of the learning curve, 
thank you for taking time to respond.
You are welcome.
Another thing I do not like about hot spares… When a drive fails, I want to be sure my external backups are good and up to date, before beginning a rebuild. Rebuilds are stressful to all drives and should another drive fail during a rebuild, the array is lost to all but expensive recovery processes.
With a hot spare, the rebuild starts “immediately”. Good luck!
I appreciate your perspective. Instead of having it set as an official hot spare, is it any different (other than not automatically rebuilding) if I have a drive plugged in but not assigned to any storage pool?
The drive will remain powered on with the NAS, and DSM will report its status. Whether it will “hibernate”, I do not know. I prefer to keep my “spares” sealed in their boxes and stored in my “bookcase”.
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