Re: [ANNOUNCE] Native Linux KVM tool v2

[Anthony Liguori <anthony@codemonkey.ws>]

On 06/15/2011 03:13 PM, Prasad Joshi wrote:
> On Wed, Jun 15, 2011 at 6:10 PM, Pekka Enberg<penberg@kernel.org>  wrote:
>> On Wed, Jun 15, 2011 at 7:30 PM, Avi Kivity<avi@redhat.com>  wrote:
>>> On 06/15/2011 06:53 PM, Pekka Enberg wrote:
>>>>
>>>> - Fast QCOW2 image read-write support beating Qemu in fio benchmarks. See
>>>> the
>>>>    following URL for test result details: https://gist.github.com/1026888
>>>
>>> This is surprising.  How is qemu invoked?
>>
>> Prasad will have the details. Please note that the above are with Qemu
>> defaults which doesn't use virtio. The results with virtio are little
>> better but still in favor of tools/kvm.
>>
>
> The qcow2 image used for testing was copied on to /dev/shm to avoid
> the disk delays in performance measurement.

Our experience has been that this is actually not a great way to 
simulate fast storage.

Spindle based storage has very different characteristics than memory as 
there is a significant cost for seeking.

-hdb uses IDE too.  That's pretty unfair since IDE is limited to a 
single request at a time whereas virtio can support multiple requests 
(and native kvm tools is using virtio).

Regards,

Anthony Liguori