On Fri, Jul 04, 2008 at 12:59:41AM -0700, Dave Chinner wrote:
> On Fri, Jul 04, 2008 at 08:41:26AM +0200, Jens Beyer wrote:
> > I have encountered a strange performance problem during some
> > hardware evaluation tests:
> > I am running a benchmark to measure especially random read/write
> > I/O on an raid device and found that (under some circumstances)
> > the performance of Random Read I/O is inverse proportional to the
> > size of the tested XFS filesystem.
> > In numbers this means that on a 100GB partition I get a throughput
> > of ~25 MB/s and on the same hardware at 1TB FS size only 18 MB/s
> > (and at 2+ TB like 14 MB/s) (absolute values depend on options,
> > kernel version and are for random read i/o at 8k test block size).
> Of course - as the filesystem size grows, so does the amount of
> each disk in use so the average seek distance increases and hence
> read I/Os take longer.
But then - why does the rate of ext3 does not decrease and stays at the