Re: [Xen-API] Fwd: Getting VM stats

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Tue, Dec 19, 2006 at 11:08:42AM -0800, jdsw wrote:
> I understand that mechanism for collecting data might be different and
> specific. But the transport and API to get that information can be 
> standardised. For example, a way to push some structured data on xenbus 
> and make it accessible  through Xend api.

Any monitoring standard though, is not going to standardize on a Xen-API
transport, because it'll obviously want to be equally appicable to non-Xen
environments. I imagine that Xen-API will be used as one data source for
collecting such monitoring data, but the monitoring data transport & arch
will be at a layer above - it would merely have a Xen-API plugin for getting
HV / VBD / VIF stats. 

Wrt to pushing stats from DomU back to Dom0 via XenBus - there's not really
any clear benefit to doing that for general perf monitoring. Monitoring systems
will typically send data off-host to a remote / centralized collection point,
so sending it from DomU -> Dom0 -> <monitor-host>, does seem to really
give any benefit over just having  DomU -> <monitor-host>. It could even be
detrimental when you think of the complication of migration which means the
undering Dom0 you're on can change at any time.

> Also, I am not sure, if the email that I fwd got other questions about, 
> how to get certain basic metrics through Xend instead of using combination 
> of Xend API, Memory Maps, parsing files for VBD and n/w information.

The Xen-API is intended to give access to stats on CPU timeslice allocated
to VMs, memory allocation, VBD & VIF  I/O stats - basically anything that is
related to the Dom0 management side of VMs. So for Xen specific stats the
Xen-API should be the primary access point, while OS specific stats the Dom0
or DomU OS can be used as with baremetal. Xen-API isn't intending to provide
general stats for Dom0 OS, since they can already be obtained with a variety
of other tools.

> "Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote: On Tue, Dec 19, 2006 at 
> 09:54:10AM -0800, jdsw wrote:
> > Do you guys have any suggestion ?
> >   (I did not get satisfactory answers to each of the questions on dev forum)
> >    
> >   In addition is there a plan for a streamlined access to things happening 
> > in Domu information through Dom0. For example: Top process information in a 
> > DomU available through Dom0 ?
> 
> The Xen-API work is really about management of Dom0 and DomU VMs as opaque
> entities viewed from Dom0. Collecting OS specific details about work going on 
> inside the DomU (eg processes running, detailed breakdown of CPU & memory
> usage) is best handled by a dedicated monitoring API. It has very different
> requirements of that of Xen-API, in particular from a performance / overhead
> POV. There are a wide variety of existing OS monitoring tools which can be
> deployed inside DomUs, Big-Sister, Nagios, Ganglia, to name but three such
> tools.


Dan.
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