[openstack-dev] [Nova] sponsor some LVM development

Premysl Kouril premysl.kouril at gmail.com
Fri Jan 22 20:49:51 UTC 2016

On 22 Jan 2016 17:43, "James Bottomley" <
James.Bottomley at hansenpartnership.com> wrote:
> On Fri, 2016-01-22 at 14:58 +0100, Premysl Kouril wrote:
> > Hi Matt, James,
> >
> > any thoughts on the below notes?
> To be honest, not really.  You've repeated stage two of the Oracle
> argument: wheel out benchmarks and attack alleged "complexity".

Sorry fo that, it is true that it is just our conclusion which is not based
on any deep analysis.

> don't really have a great interest in repeating a historical argument.
>  Oracle didn't get it either until they released the feature and ran
> into the huge management complexity of raw devices in the field, so if
> you have the resources to repeat the experiment and see if you get
> different results, be my guest.

> The lesson I took from the Oracle affair all those years ago is that
> it's far harder to replace well understood and functional file
> interfaces with new ones (mainly because of the tooling and historical
> understanding that comes with the old ones) than it is to gain
> performance in existing interfaces.

Ok, point taken. I agree this can be a problem.

> The 3x difference in the benchmarks would seem to indicate a local
> tuning or configuration problem, because it's not what most people see.
>  What the current benchmarks seem to show is about a 1-5% difference
> between the directio and the direct to block paths depending on fstype,
> how its tuned, ioscheduler and underlying device.

I will try to find problem in our configuration and re-run our benchmarks.
By chance do you have some more information (and possibly configuration)
about the bechmarks you are mentioning?

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