On Tuesday 09 January 2007 14:10, Roland Fehrenbacher wrote: > Hi, > > I have a very strange phenomena concerning read performance as tested > with iozone > (command line: iozone -Ra -n 16G -y 16384k -g 16G -i 0 -i 1): > > When running over Infiniband (gen1, openib LND), I get 400MB/s write > but only 160MB/s read. This is already a pretty low read speed > compared to write. However, it becomes much worse, if I run the same > benchmark over GigE: Here I get 105MB/s write (excellent), and only > 17MB/s!!! read. I already tried increasing > /proc/fs/lustre/llite/fs0/max_read_ahead_mb without much success > (changed from 14 to 17MB/s). Any idea how this could be improved?
take max_read_ahead_mb down to ~2 MiB, 1.4.6.1 had several problems with it's read-ahead logic that killed read performance (for default and larger vaules). /Peter > The configuration is as follows: > > - 1 MDS + 2 OSS with 2 OSTs each. > - Kernel 2.6.15.7 with Lustre 1.4.6.1 on both clients and servers.
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