[Lustre-discuss] performance tuning w/ dbench, bonnie++

Peter Grandi pg_lus at lus.for.sabi.co.UK
Thu Dec 24 05:18:00 PST 2009

[ ... ]

>> However, no matter what our configuration, dbench never shows
>> any improvement.  It never shows more than 25MB/sec, with 5
>> clients. I *KNOW* we are getting better throughput, but I
>> need to be able to prove it.

> Dbench should not be considered a performance benchmark, but
> rather only a load testing tool. The main reason dbench is
> not a good benchmark tool is that it creates and deletes files
> fairly rapidly, and if the file has never been written to disk
> before it is deleted, it wills still count this IO in the
> "bandwidth" number even though no bytes hit the disk.

To add to these wise words, I reckon that "bonnie++" is also a
poor benchmarking tool, regrettably very popular; I usually
prefer Bonnie 1.4 for quick tests or FIO for bigger ones (both
with the right options), and 'lmdd' from 'lmbench':


Unfortunately file system benchmarking requires great patience
and insight, and tool selection is part of that, including
knowing why 'dbench' or 'bonnie++' are not the best performance
testing tools.

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