On Thu, 2003-09-25 at 08:57, Christoph Klocker wrote:
> I had a look at the dd man page, but I couldn't find out how I use it to
> check the write speed, can you tell me how I should do it.
Try looking for lmdd instead, you will need to pull it off the net
as it is not a standard part of a distribution.
As for your original question, since you have 1G of memory, when
bonnie++ completes its write, a large percentage of the data is
still in ram, once you ramp up the size, the percentage is
smaller. To measure real disk performance you need to flush
out to disk, this does not totally explain your drop off, but
does explain some of it.
Two suggestions:
Run xfs_bmap -v on one of your files after the run has
completed and send us the output.
Read the xfsctl man page and look at the space
preallocation calls. You could also try O_DIRECT writes
here if you have control of the app. lmdd can be built
O_DIRECT capabable I think.
Steve
--
Steve Lord voice: +1-651-683-3511
Principal Engineer, Filesystem Software email: lord@xxxxxxx
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