[gpfsug-discuss] Looking for a way to see which node is having an impact on server?

Alex Chekholko chekh at stanford.edu
Mon Dec 9 19:52:52 GMT 2013


Hi Richard,

I would just use something like 'iftop' to look at the traffic between 
the nodes.  Or 'collectl'.  Or 'dstat'.

e.g. dstat -N eth0 --gpfs --gpfs-ops --top-cpu-adv --top-io 2 10
http://dag.wiee.rs/home-made/dstat/

For the NSD balance question, since GPFS stripes the blocks evenly 
across all the NSDs, they will end up balanced over time.  Or you can 
rebalance manually with 'mmrestripefs -b' or similar.

It is unlikely that particular files ended up on a single NSD, unless 
the other NSDs are totally full.

Regards,
Alex

On 12/06/2013 04:31 PM, Richard Lefebvre wrote:
> Hi,
>
> I'm looking for a way to see which node (or nodes) is having an impact
> on the gpfs server nodes which is slowing the whole file system? What
> happens, usually, is a user is doing some I/O that doesn't fit the
> configuration of the gpfs file system and the way it was explain on how
> to use it efficiently.  It is usually by doing a lot of unbuffered byte
> size, very random I/O on the file system that was made for large files
> and large block size.
>
> My problem is finding out who is doing that. I haven't found a way to
> pinpoint the node or nodes that could be the source of the problem, with
> over 600 client nodes.
>
> I tried to use "mmlsnodes -N waiters -L" but there is too much waiting
> that I cannot pinpoint on something.
>
> I must be missing something simple. Anyone got any help?
>
> Note: there is another thing I'm trying to pinpoint. A temporary
> imbalance was created by adding a new NSD. It seems that a group of
> files have been created on that same NSD and a user keeps hitting that
> NSD causing a high load.  I'm trying to pinpoint the origin of that too.
> At least until everything is balance back. But will balancing spread
> those files since they are already on the most empty NSD?
>
> Richard
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-- 
Alex Chekholko chekh at stanford.edu



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