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Subject: Re: [Qemu-devel] [RFC PATCH 0/9] vhost-nvme: new qemu nvme backend
 using nvme target
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, Rob Nelson <rlnelson@google.com>, Christoph Hellwig <hch@lst.de>, linux-nvme@lists.infradead.org, virtualization@lists.linux-foundation.org

On Tue, 2015-12-01 at 11:59 -0500, Paolo Bonzini wrote:
> > What do you think about virtio-nvme+vhost-nvme?
> 
> What would be the advantage over virtio-blk?  Multiqueue is not supported
> by QEMU but it's already supported by Linux (commit 6a27b656fc).

I expect performance would be better.

Seems google cloud VM uses both nvme and virtio-scsi. Not sure if
virtio-blk is also used.
https://cloud.google.com/compute/docs/disks/local-ssd#runscript

> 
> To me, the advantage of nvme is that it provides more than decent performance on
> unmodified Windows guests, and thanks to your vendor extension can be used
> on Linux as well with speeds comparable to virtio-blk.  So it's potentially
> a very good choice for a cloud provider that wants to support Windows guests
> (together with e.g. a fast SAS emulated controller to replace virtio-scsi,
> and emulated igb or ixgbe to replace virtio-net).

vhost-nvme patches are learned from rts-megasas, which could possibly be
a fast SAS emulated controller.
https://github.com/Datera/rts-megasas

> 
> Which features are supported by NVMe and not virtio-blk?

Rob (CCed),

Would you share whether google uses any NVMe specific feature?

Thanks.