[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] [Qemu-devel] RFC: use case for adding QMP, block jobs &
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [Qemu-devel] RFC: use case for adding QMP, block jobs & multiple exports to qemu-nbd ? |
Date: |
Fri, 3 Nov 2017 10:01:02 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Fri, Nov 03, 2017 at 02:00:46PM +0800, Fam Zheng wrote:
> On Thu, 11/02 12:02, Daniel P. Berrange wrote:
> > One alternative approach to doing this would be to suggest that we should
> > instead just spawn qemu-system-x86_64 with '--machine none' and use that
> > as a replacement for qemu-nbd, since it already has a built-in NBD server
> > which can do many exports at once and arbitrary block jobs.
>
> Here is a crazy idea from KVM Forum discussions that may relate, so mention it
> here: we could move the QEMU block layer to a separate program and guest can
> use
> vhost-user-{blk,scsi} for I/O. It is something like this:
>
>
> master-disk1.qcow2 (qemu-nbd)
> ^
> | backing
> |
> cache-disk1.qcow2 (qemu-vhost) <-------------.
> ^ |
> | backing | backing
> | |
> +- vm-a-disk1.qcow2 (qemu-vhost) +- vm-a-disk2.qcow2
> (qemu-vhost)
> ^ ^
> | vhost-user-blk |
> vhost-user-blk
> | |
> +- VM-1 (qemu-system-XXX) +- VM-2
> (qemu-system-XXX)
>
>
> So on the compute node, there will be N qemu-system-XXX processes (where N is
> the number of VMs) and 1 qemu-vhost process.
>
> The hypothetical qemu-vhost program needs to support QMP as well and it runs
> the
> COR/mirroring jobs from master disk to cache disk, just like what you propose
> to
> do with the extended qemu-nbd. The only difference is replacing the local NBD
> with vhost-user, which is more efficient.
The vhost-user part can be added later. I think the first step is
whether to add a QMP interface to qemu-nbd or use -machine none.
Stefan
signature.asc
Description: PGP signature
- Re: [Qemu-block] RFC: use case for adding QMP, block jobs & multiple exports to qemu-nbd ?, (continued)
Re: [Qemu-block] RFC: use case for adding QMP, block jobs & multiple exports to qemu-nbd ?, Paolo Bonzini, 2017/11/02
Re: [Qemu-block] RFC: use case for adding QMP, block jobs & multiple exports to qemu-nbd ?, Max Reitz, 2017/11/02
Re: [Qemu-block] [Qemu-devel] RFC: use case for adding QMP, block jobs & multiple exports to qemu-nbd ?, Fam Zheng, 2017/11/03
- Re: [Qemu-block] [Qemu-devel] RFC: use case for adding QMP, block jobs & multiple exports to qemu-nbd ?,
Stefan Hajnoczi <=