Mailinglist Archive: opensuse (1355 mails)

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Re: [opensuse] brtfs subvolume as VM images storage
On 11 June 2018 at 13:48, sogal <sogal@xxxxxxxxxx> 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 :)

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