Re: Providing temporary storage space to a VM: qcow, nfs etc

[David Brownlee <abs%absd.org@localhost>]

On Thu, 25 Jun 2020 at 04:32, Mayuresh <mayuresh%acm.org@localhost> wrote:
>
> I am using a Linux guest as a pkgsrc build server and the host isn't
> particularly rich in disk space. So can't completely reserve all the space
> required, but spikes in usage during compilation are accommodatable.
>
> I was using qcow2 disk image, but as someone already pointed out it fills
> up rapidly and I searched further on that - it doesn't actually delete
> anything. I don't find an easy way to compress it other than using a qemu
> tool to create a duplicate image and delete the old one.
>
> Looking for something more conservative on space. So turned to network
> file systems with the host. But they aren't particularly speedy. Here are
> speeds shown by dd for write operations:
>
> qcow2: 64MB/s - good but disk fills up rapidly, no easy way to shrink
> nfs: 9.8MB/s - about 6 to 7 times slower than virtual qcow2 disk
> sshfs: 1.8MB/s - no need as nfs does better
>
> If I could reduce the gap between nfs and qcow2 even to some extent I'd
> probably settle for that, as it gives me a lot of flexibility in storage.

A quick if not necessarily elegant option would be to have multiple
qcow2 files - one for the system and one for space to build. You can
release the build space by stopping the vm, just recreating the second
qcow2 file and restarting the VM

David