[Beowulf] clustering using xen virtualized machines

Huw Lynes lynesh at Cardiff.ac.uk
Tue Jan 26 09:48:48 EST 2010


On Tue, 2010-01-26 at 13:24 +0000, Tim Cutts wrote:

> 1)  Applications with I/O patterns of large numbers of small disk  
> operations are particularly painful (such as our ganglia server with  
> all its thousands of tiny updates to RRD files).  We've mitigated this  
> by configuring Linux on this guest to allow a much larger proportion  
> of dirty pages than usual, and to not flush to disk quite so often.   
> OK, so I risk losing more data if the VM goes pop, but this is just  
> ganglia graphing, so I don't really care too much in that particular  
> case.

Ganglia thrashes disks even on physical hardware. So I'm not sure it's
fair to lay this at the door of VMWare. We run our ganglia on physical
hardware and we still have to put the RRDs in a tmpfs partition to stop
the disk I/O grinding the server down.

Other than that your experience matches what I've seen with my ESX
system (which we don't use for HPC).

Thanks,
Huw

-- 
Huw Lynes                       | Advanced Research Computing
HEC Sysadmin                    | Cardiff University
                                | Redwood Building, 
Tel: +44 (0) 29208 70626        | King Edward VII Avenue, CF10 3NB


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