>>>>> "Peter" == Peter Kjellstrom <[EMAIL PROTECTED]> writes:
Peter> On Tuesday 09 January 2007 14:10, Roland Fehrenbacher
Peter> 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?
Peter> take max_read_ahead_mb down to ~2 MiB, 1.4.6.1 had several
Peter> problems with it's read-ahead logic that killed read
Peter> performance (for default and larger vaules).
Thanks for the hint, Peter. Unfortunately setting this to 2MB (echo 2
> /proc/fs/lustre/llite/fs8/max_read_ahead_mb) resulted in even poorer
performance of approx. 10MB/s. Any other ideas?
Roland
>> 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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