RAID1 Storage Pool w/Single Max Volume to Multiple Volumes

When I first configured my DS220+, I assigned my two 4Tb drives into a single RAID1 storage pool and single (max size) Btrfs volume. I’m using about 35% of available space.

I now know that was a big mistake as I now have a desire for a second volume to serve as an off-site Hyper Backup for a friend.

I’ve done my reading and found the following…

RAID1 storage pools can’t be changed to SHR storage pools

The volume size on RAID1 (or SHR?) storage pools can’t be reduced to make room for another volume.

It is possible to change a RAID 1 storage pool with a single Btrfs volume into multiple Btrfs volumes ONLY if there is unassigned space in the storage pool or larger drive are installed.

If the above is true, I’m stuck with only two options: Buy (2) larger drives, or rebuild the storage pool from scratch. Since I have plenty (65%) of unused space, the second option seems practical.

I do have an external 4Tb HDD purchased as a backup. And I do run regular USB Hyper Backups to it. So, theoretically, I can rebuild the storage pool from scratch.

The steps should/could be as follows:

Mount all shared drives if not already mounted

Create a new Hyper Backup of all Folders and Packages

Create new System Configuration Backup

Factory Reset NAS

Set Storage Pool as SHR

Set multiple volumes as required

Install Hyper Backup package

Restore Data and Packages from Hyper Backup to desired volume

Restore System Configuration from Backup

So, here are my questions:

Is my understanding of storage pool and volume limitations correct?

When restoring from Hyper Backup, do I have the option to restore “system configurations”?

I have read elsewhere that it is better to restore a System Configuration from backup that is not part of Hyper Backup. Is this true? And would this be the last step or before Hyper Backup restore?

Jace Elric

Participant

February 27, 2026 at 9:39 am

Your understanding is accurate. A RAID1 storage pool on the Synology DS220+ cannot be converted to SHR without deleting and recreating the pool, and a Btrfs volume that was created using the full pool size cannot be shrunk to make room for another volume. Even though only 35% of the space is used, the entire pool is already allocated to that single volume. That means your realistic options are either replacing both drives with larger ones or backing everything up and rebuilding the storage pool. Since you already have a 4TB external drive and run regular Hyper Backups, rebuilding is a workable solution. Hyper Backup can restore system configuration if it was included in the backup task, but it is generally cleaner to create a separate DSM configuration backup and restore it after your data and packages have been restored to avoid conflicts. The sensible order is: complete a final Hyper Backup, create a standalone DSM configuration backup, factory reset the NAS, recreate the pool as SHR with the volumes you need, reinstall Hyper Backup, restore your data and packages, and then restore the DSM configuration last.