On 28/02/2021 09:31, Jan-Frode Myklebust wrote:
I’ve tried benchmarking many vs. few vdisks per RG, and never could see
any performance difference.
That's encouraging.
Usually we create 1 vdisk per enclosure per RG, thinking this will
allow us to grow with same size vdisks when adding additional enclosures
in the future.
Don’t think mmvdisk can be told to create multiple vdisks per RG
directly, so you have to manually create multiple vdisk sets each with
the apropriate size.
Thing is back in the day so GPFS v2.x/v3.x there where strict warnings
that you needed a minimum of six NSD's for optimal performance. I have
sat in presentations where IBM employees have said so. What we where
told back then is that GPFS needs a minimum number of NSD's in order to
be able to spread the I/O's out. So if an NSD is being pounded for reads
and a write comes in it. can direct it to a less busy NSD.
Now I can imagine that in a ESS/DSS-G that as it's being scattered to
the winds under the hood this is no longer relevant. But some notes to
the effect for us old timers would be nice if that is the case to put
our minds to rest.
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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