Number of Columns - Storage Spaces

Hi,

I try to reorganize my File Server.

I have currently 4 Disks + 2 for OS.

This is my currently Layout:

FriendlyName        ResiliencySettingNa OperationalStatus   HealthStatus        IsManualAttach                     Size
                    me
------------        ------------------- -----------------   ------------        --------------                     ----
Temp                Simple              OK                  Healthy             False                           1.75 TB
Files-HA            Parity              OK                  Healthy             False                            926 GB

Friendlyname                                                               size                           AllocatedSize
------------                                                               ----                           -------------
PhysicalDisk5                                                     1999575711744                            497679335424
PhysicalDisk4                                                     2999766220800                            500095254528
PhysicalDisk1                                                      499289948160                            497410899968
PhysicalDisk0                                                     2999766220800                           1705638887424

If I check NumberOfColums for Files-HA I can see it has 3:

FriendlyName                      : Files-HA
HealthStatus                      : Healthy
Interleave                        : 262144
IsDeduplicationEnabled            : False
IsEnclosureAware                  : False
IsManualAttach                    : False
IsSnapshot                        : False
LogicalSectorSize                 : 4096
Name                              :
NameFormat                        :
NumberOfAvailableCopies           :
NumberOfColumns                   : 3
NumberOfDataCopies                : 1
OperationalStatus                 : OK
OtherOperationalStatusDescription :
OtherUsageDescription             :
ParityLayout                      : Rotated Parity
PhysicalDiskRedundancy            : 1But if I check the Disc in the GUI I see 4 physical Discs in use;

When Files-HA was created there were only 3 Discs.

My understanding is, that NumberOfColumns equals number of Discs in use.

So I tried to create a new virtual Disc that uses 4 columns - a very small one:

Get-StoragePool Pool1 | New-VirtualDisk -FriendlyName Files-1 -ResiliencySettingName "Parity"
 -size 3GB -NumberOfColumns 4
New-VirtualDisk : There are not enough eligible physical disks in the storage pool to create the specified virtual
disk configuration.
At line:1 char:25+ Get-StoragePool Pool1 | New-VirtualDisk -FriendlyName Files-1 -ResiliencySetting ...+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : InvalidOperation: (StorageWMI:ROOT/Microsoft/...SFT_StoragePool) [New-VirtualDisk], CimE
   xception+ FullyQualifiedErrorId : StorageWMI 48004,New-VirtualDisk

And one more question - is there a way to shrink a virtual Disc if the volume does not use the space?

Currently I have to work with multiple virtual discs because of the different sizes. I will replace the Disc step by step so later I will hopefully have 4 x 3TB with one virtual Disc and parity.

But now I want to have

1.) Disc with Parity 4 x 500GB (1.5TB netto)

2.) Disc with Parity 3 x 1.5TB (3TB netto)

3.) Disc with Mirror 2 x 1TB (1 TB netto)

thx in advance