[gpfsug-discuss] High I/O wait times

Jonathan Buzzard jonathan.buzzard at strath.ac.uk
Sat Jul 7 09:42:57 BST 2018


On 07/07/18 01:28, Buterbaugh, Kevin L wrote:

[SNIP]

> 
> So, to try to rule out everything but the storage array we replaced the 
> FC cables going from the SAN switches to the array, plugging the new 
> cables into different ports on the SAN switches.  Then we repeated the 
> dd tests from a different NSD server, which both eliminated the NSD 
> server and its’ FC cables as a potential cause … and saw results 
> virtually identical to the previous test.  Therefore, we feel pretty 
> confident that it is the storage array and have let the vendor know all 
> of this.

I was not thinking of doing anything quite as drastic as replacing 
stuff, more look into the logs on the switches in the FC network and 
examine them for packet errors. The above testing didn't eliminate bad 
optics in the storage array itself for example, though it does appear to 
be the storage arrays themselves. Sounds like they could do with a power 
cycle...

JAB.

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



More information about the gpfsug-discuss mailing list