Just a heads-up that the 3.10 kernel in CentOS/RHEL is *not* a stock 3.10
kernel. It has had many things backported from later kernels, though they may
not have backported the specific improvements you're looking for.
I think CentOS is using qemu 2.3, which is pretty new. Not sure how new their
libiscsi is though.
Chris
On 03/07/2016 12:25 AM, Preston L. Bannister wrote:
Should add that the physical host of the moment is Centos 7 with a packstack
install of OpenStack. The instance is Ubuntu Trusty. Centos 7 has a relatively
old 3.10 Linux kernel.
From the last week (or so) of digging, I found there were substantial claimed
improvements in /both/ flash support in Linux and the block I/O path in QEMU -
in more recent versions. How much that impacts the current measures, I do not
(yet) know.
Which suggests a bit of tension. Redhat folk are behind much of these
improvements, but RHEL (and Centos) are rather far behind. Existing RHEL
customers want and need careful, conservative changes. Folk deploying OpenStack
need more aggressive release content, for which Ubuntu is currently the best
base.
Will we see a "Redhat Cloud Base" as an offering with RHEL support levels, and
more aggressive QEMU and Linux kernel inclusion?
At least for now, building OpenStack clouds on Ubuntu might be a much better
bet.
Are those claimed improvements in QEMU and the Linux kernel going to make a
difference in my measured result? I do not know. Still reading, building tests,
and collecting measures...
On Thu, Mar 3, 2016 at 11:28 AM, Chris Friesen <chris.frie...@windriver.com
<mailto:chris.frie...@windriver.com>> wrote:
On 03/03/2016 01:13 PM, Preston L. Bannister wrote:
> Scanning the same volume from within the instance still gets the
same
> ~450MB/s that I saw before.
Hmmm, with iSCSI inbetween that could be the TCP memcpy limitation.
Measuring iSCSI in isolation is next on my list. Both on the physical
host, and
in the instance. (Now to find that link to the iSCSI test, again...)
Based on earlier comments it appears that you're using the qemu built-in
iSCSI initiator.
Assuming that's the case, maybe it would make sense to do a test run with
the in-kernel iSCSI code and take qemu out of the picture?
Chris
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