So I had automatic decryption of my drives working with a normal OMV-install.
I was trying to setup btrfs snapshots and for this reason installed Debian and then OMV.
Everything is working fine except for my crypttab.
During initramfs it says: "cryptsetup: Waiting for encrypted source device UUID=...."
Calling `blkid` (inside initramfs after the timeout) shows that no block device (other then my root device) is available and therefore cannot be decrypted ....
I run out of ideas.
I also installed to a ext4 partition and I have the same problem, so its not btrfs causing the issue.
Before updating the initramfs with crypttab the drives show up fine once booted and I am able to decrypt and mount them inside the WebUI.
Something is missing in the initramfs which is causing the drives not to load during this stage...