What's the recommended way to manage a bunch of VMs? Is ZFS on host and in the VM a problem with COW on COW and write amplification and all? ZVOLs? raw images? SSD TRIM (not needed on spinning rust?)?
ZVOLs seem nice except for
A zvol’s used can exceed what the guest believes it is using, sometimes dramatically. ...which netbsd does not support, unless ZFS somehow can without fstrim (which wouldn't surprise me since ZFS seems happy to implement its own things).
The fix is discard/TRIM from the consumer:
If ZFS on ZFS is not ideal, then is mounting FFS with sync as safe as you can make it? It was not difficult to make fschk fail in the test VM without that (It got stuck booting on a black screen while pinning all cores to 100% for a minute for no easily discernible reason. Killed the VM and restarted it, and fschk failed.)
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