Hi Richard, Le lundi 11 juin 2018 à 01:52:56, Richard Brown a écrit :

On 11 June 2018 at 13:48, sogal <sogal@volted.net> wrote:

...

Hi all,

I have a project of a small home server that I will use as an hypervisor. I was wondering if there is any advantages (except the ones natively provided by btrfs itself) or drawbacks using a btrfs subvolume as VM (qcow files) images storage ? Or if there is some mount options to add for performance purpose ? This storage will host four or five 40G qcow files.

Using btrfs with copy-on-write ENABLED is not advisable for qcow VM file storage

The performance problem is pretty easy to consider - having copy-on-write enabled on btrfs PLUS in qcow will double the number of copy-on-write calls for every write ;)

That is why openSUSE installations disable CoW for /var where we expect VM qcow images to be stored

But that has the drawbacks of disabling any of the CoW-dependant features of btrfs

So in short

1. If you're putting your qcows in a standard openSUSE /var subvolume - no problem 2. If you're making your own btrfs subvolume/partition - disable CoW or consider a different filesystem

Good luck :)

Thanks a lot for this detailed answer. I have no plan to use another subvolume, I will stick to the filehier and use the default /var/lib/libvirt and, therefore, the openSUSE config. Thank you ! Cheers, -- Sébastien 'sogal' POHER -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org