Subject: Re: [vserver] tcpdump, top, mpstat, iostat
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Fri, 7 Jan 2011 04:27:54 +0100

On Fri, Jan 07, 2011 at 10:35:12AM +0900, Andrej van der Zee wrote:
> Dear Herbert,

> Thanks again.

> > note that I do not see a good reason to do that
> > accounting for or from within a guest, if you want
> > to monitor I/O to devices, IMHO the host is the best
> > place to do so (same for network statistics)

> I have (not yet) used vserver. But let me test my understanding. 
> if I run tcpdump on the host, I sniff all the network packets 
> for a NIC shared among all its guests. 

right.

> Therefor with some tcpdump-filters it should be possible to
> isolate packets for one specific guest, right? 

right again.

> Any ideas what parameters I could use that are guest-specific 
> such as (virtualized) IP address, MAC-address, ...?

as the default setup uses IP isolation, you assign a
subset of host IPs to each guest, assuming that those
IPs do not overlap, your filter would be simply the
IPs assigned to the guest in question.

> In case of IO device stats, suppose every guest has its own 
> physical device, running iostat on the host for one specific 
> device would isolate usage for the guest that it owns. 
> Is this correct?

yes, but would be a waste of resources (to have a
separate device for each guest).

> > so, unless somebody finds this feature so increadibly
> > usefull that s/he decides to sponsor development in
> > this direction, I doubt it will ever get implemented.

> I wish I had a money-tree in my garden ;)

yep, that would be nice :)

HTC,
Herbert

> Thank you,
> Andrej