On Tue, 2007-06-12 at 13:12 +0000, salmr0@xxxxxx wrote:
> Thanks that helps. Now that I know I have the right sunit and swidth
> I have a performace related question.
> If I do a dd on the raw device or to the lun directy I get speeds of
> around 190-200 MBytes/sec.
> As soon as I add xfs on top of the lun my speeds go to around 150
> MBytes/sec. This is for a single stream write using various block
> sizes on a 2 Gbit/sec fiber channel card.
Reads or writes?
What are your I/O sizes?
Buffered or direct IO?
Including fsync time in there or not? etc, etc.
(Actual dd commands used and their output results would be best)
xfs_io is pretty good for this kind of analysis, as it gives very
fine grained control of operations performed, has integrated bmap
command, etc - use the -F flag for the raw device comparisons).
> Is this overhead more or less what you would expect from xfs? Or is
> there some tunning I need to do?
You should be able to get very close to raw device speeds esp. for a
single stream reader/writer, with some tuning.