Re: Journalling in VM?

On Feb 20, 8:48 pm, Tim Roberts <t...@xxxxxxxxx> wrote:

Is there any point to running a journalling file system inside a virtual
machine?

Absolutely. Precisely the same reasons to do so in a regular machine.

As long as the host machine has a reliable file system, even if
the host crashes, the memory image should be recoverable so that the VM's
file system survives.

Umm, huh? What does the memory image have to do with the disk image?
The problem would be the vm crashing with its disk image in an
inconsistent state. Even if the host is perfect, it would simply
perfectly reflect the inconsistent disk image at the time the vm
crashed.

There are certainly scenarios in which the file system might not close
cleanly, but I'm wondering whether the probability is so low that the
overhead of journalling doesn't pay.

If so, that would be the same with a regular machine and a virtual
machine. The issues are precisely the same, with the possible
exception that the vulnerability window might be a bit greater for a
virtual machine.

The virtual machine can still crash with an inconsistent disk image
due to unflushed data. The vm software can induce a crash where bare
metal hardware would have been fine (yes, vms have bugs).

DS
.