Re: [Xen-users] Xen resource guarantees

To:	rbp@xxxxxxxxxxxxx
Subject:	Re: [Xen-users] Xen resource guarantees
From:	"Henning Sprang" <henning_sprang@xxxxxx>
Date:	Thu, 30 Nov 2006 21:18:10 +0100
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On 11/30/06, Rodrigo Borges Pereira <rbp@xxxxxxxxxxxxx> wrote:

>From my point of view, this paragraph gives the impression that Xen provides 
QoS mechanisms for managing VM resource allocation at
all levels. However, i'm having a hard time figuring out how does Xen provide 
and allows for management those resource guarantees,
particularly regarding block I/O.


I am also interested in this topic, currently a bit more from the
viewpoint of monitoring these things (as can be seen in my posts here
some days ago and on xen-devel today), for example to tell when
ressources are exhausted or satured in order to drive things like
deployment and migrations decisions based on the data.

I found in this paper, with a study and examples:
http://www.hpl.hp.com/techreports/2006/HPL-2006-77.ps,  which is
mainly for Net I/O I didn't checkl if Shareguard and SEDF-DC code is
in the Xen unstable code yet.
I didn't come so far yet to find more information especially on Disk I/O.

Maybe there can be found some more information on the Xen summit
pages: http://xensource.com/xen/xensummit.html.

Finally, I think giving guarantees might be easier than the monitoring
and measuring I intend - you can "simply" (much simplified, I have no
ready solution but think it's easier) measure I/O throughput, and if a
domain can't get to it's guaranteed level, (aasumed it's actually
trying to use the ressources), the guarantee isn't met and measures
need to be taken - other domains need to be scheduled down, or a
migration to more powerful hardware is needed.

Henning

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