Storage Spaces Direct Windows Server 2016 transient error

Speaking shortly, the deployment sequence looks as following:

1. Deploy necessary WS roles and features
2. Validate the Failover Cluster
3. Create the Failover Cluster
4. Enable Storage Spaces Direct

-EnableStorageS2D

5. Create and configure storage pools

Example input:

New-StoragePool -StorageSubSystemName #CLUSTER_NAME# -FriendlyName #POOL_NAME# -WriteCacheSizeDefault 0 -ProvisioningTypeDefault Fixed -ResiliencySettingNameDefault Simple -PhysicalDisk (Get-StorageSubSystem -Name #CLUSTER_NAME# | Get-PhysicalDisk)

6. Create and configure virtual disks

Example input:

New-Volume -StoragePoolFriendlyName #POOL_NAME# -FriendlyName #VD_NAME# -PhysicalDiskRedundancy 2 -FileSystem CSVFS_REFS –Size 100GB

7. Deploy SOFS
8. Create file shares That's it!

Here are two articles that I found helpful:

Link1 https://www.starwindsoftware.com/blog/microsoft-storage-spaces-direct-4-node-setup-2

Link2 https://technet.microsoft.com/en-us/windows-server-docs/storage/storage-spaces/hyper-converged-solution-using-storage-spaces-direct

I have found my own mistake.

I initially used a variable to define whichs physical disk should be used for my virtualdisks.

I wanted to use only HDDs, so

$disks = Get-PhysicalDisk | ? {$_.MediaType -eq 'HDD'}

Then I wanted to create my virtual disk.

New-VirtualDisk -FriendlyName vDisk -ResiliencySettingName Mirror -StoragePoolFriendlyName Pool -Size 930GB -PhysicalDisksToUse $disks

I did not think about my first command, Get-PhysicalDisk does return the system drive too - and not only the disks in the pool !

Somehow the cmdlet "New-VirtualDisk" was able to create a virtual disk with the system drive in $disks-array.. - I don't think that should be possible

I should have defined my variable as

$disks = Get-StoragePool -FriendlyName Pool | Get-PhysicalDisk | ? {$_.MediaType -eq 'HDD'}