On Mar 27, 2015, at 10:47 AM, John Nielsen <li...@jnielsen.net> wrote:

> On Mar 27, 2015, at 3:46 AM, Alexander Motin <m...@freebsd.org> 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.

Okay, some belated googling reminded me that this has been listed as an "open 
task" in the last couple of FreeBSD quarterly status reports and discussed at 
one or more devsummits. I'd still be interested to know if anyone's actually 
contemplated or started doing the work though. :)


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