Re: [Qemu-devel] qcow2: slow internal snapshot creation

[Alexandre DERUMIER <aderumier@odiso.com>]

>>Can you post more details about your benchmark setup so that this can be 
>>reproduced? And does it reproduce with local files as well or only using 
>>NFS?

Sure, I have redone tests, here the results:
(note that my netapp san have a nvram journal, so directio are as fast than buffered io)

preallocated vs non preallocated have a ratio of 5/1 for local, and 10/1 for nfs.



directio bench
---------------
fio --filename=/dev/vdb --direct=1 -rw=randwrite --bs=4K --size=5G --iodepth=100 --group-reporting --name=file1 --ioengine=libaio

buffered io bench
------------------
fio --filename=/dev/vdb --direct=1 -rw=randwrite --bs=4K --size=5G --iodepth=100 --group-reporting --name=file1 --ioengine=libaio


results
-------
local raw file
---------------
cache=none, directio, 9000 iops
cache=none,  buffered io, 10000 iops

local qcow2 preallocated
--------------------------
cache=none, directio, 8000 iops
cache=none, buffered io, 9000 iops

local qcow2 non preallocated
-----------------------------
cache=none, directio, 1400 iops
cache=none, buffered io, 2000 iops




nfs rawfile (netapp with nvram journal)
----------------------------------------
cache=none, directio, 15000 iops
cache=none,  buffered io, 15000 iops


nfs qcow2 preallocated (netapp with nvram journal)
-------------------
cache=none, directio, 12000 iops
cache=none, buffered io, 12000 iops

nfs qcow2 non preallocated (netapp with nvram journal)
-----------------------------------------------------
cache=none, directio, 1500 iops
cache=none, buffered io, 1500 iops






Alexandre D e rumier

Ingénieur Systèmes et Réseaux


Fixe : 03 20 68 88 85

Fax : 03 20 68 90 88


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----- Mail original -----

De: "Kevin Wolf" <kwolf@redhat.com>
À: "Alexandre DERUMIER" <aderumier@odiso.com>
Cc: "Dietmar Maurer" <dietmar@proxmox.com>, qemu-devel@nongnu.org
Envoyé: Vendredi 23 Novembre 2012 15:58:09
Objet: Re: [Qemu-devel] qcow2: slow internal snapshot creation

Am 23.11.2012 15:17, schrieb Alexandre DERUMIER:
>>> Preallocation doesn't matter much these days.
>
> I have done benchmark through nfs on a netapp san, (with directio),
>
> I got 300 iops without preallocation, and 6000 iops with preallocation ....

This doesn't sound right, even for writethrough modes.

Can you post more details about your benchmark setup so that this can be
reproduced? And does it reproduce with local files as well or only using
NFS?

Kevin