My mistake, for some reason i thought hdparm -T was reading from the
drives buffer, which its not.
I have done tests with bonnie++ and tiobench which also suggest there is
a bottleneck or saturation point when using ide devices concurrently.
tiotest shows on my system a 4 way ide raid0 array has slower read time
than a single drive, but i was trying to narrow down wether slowed down
by concurrent ide or raid code.
Ill try and get some more concrete results before posting them.
Thanks
Glenn
Andre Hedrick wrote:
>
> Andrew, not my utility, take it up with the author.
>
> On Wed, 14 Jun 2000, Andrew Sharp wrote:
>
> > I think you're biggest problem right now is that you aren't getting useable data
> > from hdparm. According to my man page, -T is for testing throughput of the Linux
> > buffer cache, and is supposed to avoid going to the disk all together, so I'm not
> > sure why you would bother with that test. If you want to get some numbers that
> > are more representative of what kind of throughput you can expect from your disk
> > subsystem, try a more varied benchmark approach. Do some bonnie, bonnie++ and so
> > on to get more results. Remember that a lot of IDE disks are substantially
> > cheaper than SCSI because the non-interface components are cheaper as well. A
> > lot of drive makers just slapped ide66 interfaces on the same HDA assemblies that
> > were never designed to get more than 10MB/s sustained, if that. So what you may
> > be seeing is that in raid mode you are getting more realistic results vis-a-vis
> > the actual performance capabilities of the drives themselves.
> >
> > In fact, considering the tests that you are running, the results seem quite
> > predictable. The -T mode is basically limited by the processing speed of the
> > kernel and the underlying memory architecture. So the speeds get slower the more
> > disks you add to the raid, because more CPU time is spent calculating raid
> > schtuff. I don't know how a raid0 device with just one disk works exactly, but
> > do you list results for such a beast.
> >
> > I think you'll find the results more satisfying (ie., better for 4 drives than
> > for two) if you run a test that actually does a _lot_ of reading and writing to
> > the platters themselves to get results, like a bonnie.
> >
> > a
> >
> >
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