Let's say my host disk is using EXT4, I place an image-file for my virtual machine in either QCOW2 or RAW format which again is formatted with EXT4 inside. Wouldn't journal data be written twice? First in the guest drive and then on the host? Can I safely disable journal in one of them? Or should I use a combination of two different filesystems on host and guest (if both are Linux). If guest is Windows using NTFS, which also seem to be a journal-like filesystem, could I safely disable journal on host EXT4 FS?
Maybe yet another reason to assign block-device to your VM e.g LVM as you only have one filesystem.
I do have UPS on my servers but I'm still not sure if I should disable journal completely.
