[gpfsug-discuss] Advice on NSD Thread tuning, moving from Disk to Flash

[Oesterlin, Robert]

I'm experimenting with moving some of our more heavily used files (about 5% of the file system) from disk to a flash tier. The disk latency is around 10ms, while the flash is less than 1ms. What I'm seeing that when I move the files to flash, my NSD server queues (thread queues) have a much larger number of pending RPCs. (on the Small queues) Not surprising, since the storage subsystem is faster, the clients push more requests and the NSD server backs up. I don't see an evidence of the NSD server itself running out of steam (CPU below 20%) so I'm thinking I just need to adjust the number of threads and the threads per queue. Right now I have this:


nsdMaxWorkerThreads=256, nsdMinWorkerThreads=256, nsdThreadsPerQueue=8, nsdSmallThreadRatio=1


What I'm trying to decide is whether I should increase just the MaxThreads or both the MaxThreads and the ThredsPerQueue.

Can anyone offer advice? I did read through Yuri’s document.


Bob Oesterlin
Sr Storage Engineer, Nuance HPC Grid
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