Windows 10 Pro 2004 - Removing a disk from fully mirrored Storage Pool is not possible - low space

Regular Contributor

Scenario:
Windows 10 2004
1 Storage Pool
Storage Pool functional level: vServerNext

Pool consists of 2 x 6TB same Harddisk

2 virtual Disks (DATA, BACKUPS)
Thin provisioned, NTFS, Default Cluster size
The pool usage was 4,81 TB out of 10,9 TB (before adding a 3rd disk)
Disk usage was balanced 43-44,1%
Defrag Storage Space efficiency (slab consolidation) is 98%-99%

What I am trying to do:
I need to remove one disk for maintenance
As the virtual disks are both mirrored I suspect this would be possible, but it is not.

What I did so far:
#save object of disk
$PDtoRemove = Get-PhysicalDisk -serialnumber SerialNr

#set disk as retired for removal
Set-PhysicalDisk $PDtoRemove -Usage Retired

#idenfity the used virtual disks for this physical disk
Get-PhysicalDisk $PDtoRemove | Get-VirtualDisk

#prepare for drive removal
Repair-VirtualDisk -FriendlyName 'Data'
Repair-VirtualDisk -FriendlyName 'Backups'

What troubles me:
#check jobs
Get-StorageJob
Shows both repair jobs as suspended. GUI shows - needs more disk space.

Removing the disk with
Remove-PhysicalDisk $PDtoRemove

Output:
 

- Not enough available capacity
Storage pool dos not have sufficient capacity to relocate data from the specified disk
(remark: see Job suspended)
recommended actions:
- add more physical disks to the storage pool, S
- free capacity by deleting unneeded virtual disk

This leaves me alone if I understood the concept of Storage Spaces Mirror, is equivalent of RAID 1, where I could remove / fail one drive anytime. Even more here the capacity has not even reached 50%

What I expect to happen
For a mirror, expect some metadata overhead for the pool and virtual volume this should not make a different, imho. It should tolerate this operation or a fail.

I don't want to imagine what happened if a drive really failed out of the blue.

2 Replies

I have now added a 2 TB drive and the StorageJob are now running, but the base question is why this is neccessary technically in the first place. 

Ultimately I had to supply drives of the same size of the 6TB drive I want to remove.

I have added a 2 TB internal and 3 TB USB 3.0.

So basically the effective use of what I am going to remove.
Then I was able to remove the drive marked retired.

Still question unanswered why one cannot remove a mirrored drive. If it was striped or distributed I would understand this behaviour.