[Lustre-discuss] Single client performance

[David Simas]

Hello,

I've got a Lustre system where I'd like to improve single client write
performance,  The Lustre manual reads "Lustre single client node throughput 
has been measured at 2 GB/s (max)" (section 1.1.1 Lustre Key Features),
and the web site 

	http://docs.hp.com/en/SFSUGG3-D/apas02.html?btnPrev=%AB%A0prev

indicates single client write performance of around 400 MB/s.  On my
system, I can barely get 100 MB/s for writes (measured with iozone).

I'm using Lustre 1.8.2-ext4 on RHEL5 x86_64.  I've got four OSSs each
with one OST, in hardware RAID 6.  Lustre runs on a 10 Gb network 
between the servers and clients.  For the OSSs, iozone tells me that
I can write into ext4 on the RAID arrays I configured at 750 MB/s.
Indeed, the write peformance of ext4 vs. ext3 is one reason I'm using
1.8.2-ext4.  I can also confirm (using ttcp) that the 10 Gb network
between the clients and severs can do 750 MB/s.  So I don't think that
the network or disk/controller/RAID configurations are holding me
back.

I've tried stripping across 1, 2, 3, and 4 OSTs, without much difference
in results.  I've tried disabling synchronous journals on the OSSs, and
disable the OSTs' write-through cache, again to little effect.  Should
I try the client I/O RPC stream tunables next?

The goal here is to use a Lustre file system as a sort of buffer in a 
data acquisition system.  The file system needs to support 4 - 24 input 
streams writing at 250 MB/s.  I realize that Lustre wasn't designed for 
this sort of workload.  But if I could get it to work, it would simplify 
the data acquisition pipeline.

I'm grateful for any advice.

David Simas

system.