[gpfsug-discuss] Services on DSS/ESS nodes

Jonathan Buzzard jonathan.buzzard at strath.ac.uk
Mon Oct 5 14:39:12 BST 2020


On 05/10/2020 09:40, Simon Thompson wrote:
>> I now need to check IBM are not going to throw a wobbler down the
>> line if I need to get support before deploying it to the DSS-G
>> nodes :-)
> 
> I know there were a lot of other emails about this ...
> 
> I think you maybe want to be careful doing this. Whilst it might work
> when you setup the DSS-G like this, remember that the memory usage
> you are seeing at this point in time may not be what you always need.
> For example if you fail-over the recovery groups, you need to have
> enough free memory to handle this. E.g. a node failure, or more
> likely you are upgrading the building blocks.

I think there is a lack of understanding on exactly how light weight 
keepalived is.

It's the same code as on my routers which are admittedly different CPU's 
(MIPS to be precise) but memory usage (taking out shared memory usage - 
libc for example is loaded anyway) is under 200KB. A bash shell uses 
more memory...

> 
> Personally I wouldn't run other things like this on my DSS-G storage
> nodes. We do run e.g. nrpe monitoring to collect and report faults,
> but this is pretty lightweight compared to everything else. They even
> removed support for running the gui packages on the IO nodes - the
> early DSS-G builds used the IO nodes for this, but now you need
> separate systems for this.
> 

And keepalived is in the same range as nrpe, which you do run :-) I have 
seen nrpe get out of hand and consume significant amounts of resources 
on a machine; the machine was ground to halt due to nrpe. One of the 
standard plugins was failing and sitting their busy waiting. Every five 
minutes it ran again. It of course decided to wait till ~7pm on a Friday 
to go wonky. By mid morning on Saturday it was virtually unresponsive, 
several minutes to get a shell...

I would note that you can run keepalived quite happily on an Ubiquiti 
EdgeRouter X which has a dual core 880 MHz MIPS CPU with 256MB of RAM. 
Mikrotik have models with similar specs that run it too.

On a dual Xeon Gold 6142 machine the usage of RAM and CPU by keepalived 
is noise.


JAB.

-- 
Jonathan A. Buzzard                         Tel: +44141-5483420
HPC System Administrator, ARCHIE-WeSt.
University of Strathclyde, John Anderson Building, Glasgow. G4 0NG



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