Bhyve storage improvements (was: Several bhyve quirks)

John Nielsen lists at
Fri Mar 27 16:54:44 UTC 2015

On Mar 27, 2015, at 3:46 AM, Alexander Motin <mav at> wrote:

>> I've always assumed virtio driver > emulated driver so it didn't occur
>> to me to try ahci-hd.
> I've just merged to FreeBSD stable/10 branch set of bhyve changes that
> should significantly improve situation in the storage area.
> virtio-blk driver was fixed to work asynchronously and not block virtual
> CPU, that should fix many problems with performance and interactivity.
> Both virtio-blk and ahci-hd drivers got ability to execute multiple (up
> to 8) requests same time, that should proportionally improve parallel
> random I/O performance on wide storages.  At this point virtio-blk is
> indeed faster then ahci-hd on high IOPS, and they both are faster then
> before.
> On the other side ahci-hd driver now got TRIM support to allow freeing
> unused space on backing ZVOL. Unfortunately there is no any TRIM/UNMAP
> support in virtio-blk API to allow the same.
> Also both virtio-blk and ahci-hd drivers now report to guest logical and
> physical block sizes of underlying storage, that allow guests properly
> align partitions and I/Os for best compatibility and performance.

Mav, thank you very much for all this great work and for the concise summary. TRIM on AHCI makes it compelling for a lot of use cases despite the probable performance hit.

Does anyone have plans (or know about any) to implement virtio-scsi support in bhyve? That API does support TRIM and should retain most or all of the low-overhead virtio goodness.


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