On 10/05/2020 14:28, Jaime Pinto wrote:
The rationale for my suggestion doesn't have much to do with the central
DNS server, but everything to do with the DNS client side of the service.
If you have a very busy cluster at times, and a number of nodes really
busy with 1000+ IOPs for instance, so much that the OS on the client
can't barely spare a cycle to query the DSN server on what the IP
associated with the name of interface leading to the GPFS infrastructure
is, or even process that response when it returns, on the same interface
where it's having contentions and trying to process all the gpfs data
transactions, you can have temporary catch 22 situations. This can
generate a backlog of waiters, and eventual expelling of some nodes when
the cluster managers don't hear from them in reasonable time.
It's doesn't really matter if you have a central DNS server in steroids.
If that is the scenario it will struggle to look up the DNS to IP lists
in /etc/hosts. GPFS itself will struggle to get scheduled. Besides which
systemd is caching it all locally anyways which will get hit *before*
/etc/hosts does. In an none systemd install then most likely nscd is
running which provides similar service. You don't appear to a full grasp
of how it hostname to IP resolution works.
It is a outdated notion to suggest using a system that was deprecated
over 30 years ago that needs stomping on because it comes from IMHO a
lack of seeing the whole picture.
Finally as I understand it GPFS maintains it own hostname to IP lookup
table which makes it a completely moot point. You can see this from the
fact you cannot change the IP address of a node in a cluster. You must
remove it and then rejoin with the new IP address. If it was storing
client information as hostnames and using hostname to IP resolution to
work out the IP addresses that would not be the case.
As such your suggestion is dreaming up a solution to a none existent
problem, which makes it an even worse idea IMHO.
JAB.
--
Jonathan A. Buzzard Tel: +44141-5483420
HPC System Administrator, ARCHIE-WeSt.
University of Strathclyde, John Anderson Building, Glasgow. G4 0NG
_______________________________________________
gpfsug-discuss mailing list
gpfsug-discuss at spectrumscale.org
http://gpfsug.org/mailman/listinfo/gpfsug-discuss
