Edit: retested with RC6   Installing VMs on XFS array drives workes fine, same for BTRFS cache drive. No corruption found on the qcow2 vdisks so far with the same testings as before. Already existing qcow2 images with compression which got corrupted before in RC1-4 are shown no issues so far. Will have a look at it the next couple days. Compressing an uncompressed qcow2 also not producing corrupted vdisks. Looks like the patches on qemu 4.1.1 fixed my issues.   --------------