Open Stack

After some benchmarking with random write loads we decided to go for RAW for a subset of hypervisors.
These hypervisors run only flavors for heavy IO workloads (databases).

On SSDs I noticed a performance increase (IOPS) for RAW vs QCOW of a factor 8-10.
I was somewhat surprised by the difference.
There might be something fishy in our setup because the general consensus seems to be QCOW should not
impact performance that much.
Maybe it has something to do with SSDs or because we have no RAID controllers with caching..

For us, with QCOW, the hypervisor seem to be limited by (also) doing lots of reads when writing.
( I'm running CentOS. )

I'd do some performance testing for your expected workload.
Starting a vm and doing a fio benchmark is not that time intensive :)

Cheers,
Robert van Leeuwen



________________________________
From: Nhan Cao [nhanct92 at gmail.com]
Sent: Tuesday, July 08, 2014 5:27 AM
To: openstack at lists.openstack.org
Subject: [Openstack] which image format you use for qemu?

hi guys,
i have a question.
which format to use for qemu hypervisor for performance - raw or qcow2?
Thanks
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