[Lustre-discuss] One or two OSS, no difference?

[Oleg Drokin]

Hello!

On Mar 3, 2010, at 6:35 PM, Jeffrey Bennett wrote:
> We are building a very small Lustre cluster with 32 clients (patchless) and two OSS servers. Each OSS server has 1 OST with 1 TB of Solid State Drives. All is connected using dual-port DDR IB.
>  
> For testing purposes, I am enabling/disabling one of the OSS/OST by using the “lfs setstripe” command. I am running XDD and vdbench benchmarks.
>  
> Does anybody have an idea why there is no difference in MB/sec or random IOPS when using one OSS or two OSS? A quick test with “dd” also shows the same MB/sec when using one or two OSTs.

I wonder if you just don't saturate even one OST (both backend SSD and IB interconnect) with this number of clients? Does the total throughput decreases as you decrease
number of active clients and increases as you increase it even further?
Increasing maximum number of in-flight rpcs might help in that case.
Also are all of your clients writing to the same file or each client does io to a separate file (I hope)?

Bye,
    Oleg