[Lustre-discuss] performance tuning

[Martin Pokorny]

Hello all,

I'm in the process of evaluating Lustre for a project I'm working on, 
and I'd like to ask for some advice on tuning my configuration for 
better performance. For my evaluation work, I've got one MGS/MDS and 
four OSSes each hosting one OST. This storage cluster was put together 
using some spare nodes that we had from a small, currently unused 
compute cluster, and the disks are all single scsi drives. All of the 
Lustre servers are running 2.6.18-92.1.17.el5_lustre.1.8.0smp kernels, 
and the clients are patchless. All networking is over 1Gb Ethernet.

In our application we have an instrument streaming data to a (compute) 
cluster, which then does some work and writes results to a file, all of 
which generally has to occur in real time (that is, keep up with the 
streaming data). The files are written by processes running on the 
cluster concurrently; that is, for a particular data set, multiple 
processes are writing to one file. Due to the way the instrument 
distributes data to the cluster nodes, as well as the format of output 
files, each cluster process generally writes a relatively small amount 
of data in a block, but at a high frequency (about every 10-100ms). It 
might be important to note that the blocks written by a single process 
are not in general contiguous. The aggregate data rate being written to 
the output files is approximately 100MB/s at this time, although this 
may ramp up considerably at a later date.

While my brief testing with IOR showed acceptable write throughput to 
the Lustre filesystem, I have been unable to achieve anywhere near that 
figure with our application doing the writes --- I'm concerned that the 
write pattern being used is a severely limiting factor. In this 
situation, does anyone have any advice about what I ought to be looking 
at to improve performance on Lustre?

-- 
Martin