[sclug] disk transfer rates (was) Newbie, partitioning 120Gb HDD - recommendations?

[Tom Dawes-Gamble]

On Wed, 2005-01-19 at 16:26 +0000, Alex Butcher wrote:
> On Wed, 19 Jan 2005, Tom Dawes-Gamble wrote:
> 
> > On Wed, 2005-01-19 at 13:38 +0000, Dickon Hood wrote:
> >> On Wed, Jan 19, 2005 at 12:02:52 +0000, Tom Dawes-Gamble wrote:
> >> : On Wed, 2005-01-19 at 10:09 +0000, Dickon Hood wrote:
> >> : > On Wed, Jan 19, 2005 at 07:52:42 +0000, Tom Dawes-Gamble wrote:
> >>
> >> : > [...]
> >>
> >> : > : So I've knocked together a very rough benchmark. How long so it take to
> >> : > : read a gigabyte from the disk.  I did each test several times and these
> >> : > : are typical results.
> >>
> >> Well, yes, of course.  And hdparm is a userland tool as well, it just uses
> >> the exposed ATAPI API to talk to the discs directly.
> >>
> >
> > But I'm not going to use that API in my programmes so it's not measuring
> > what I want to measure.
> 
> That's all very well, providing you know that you're going to be performing
> exactly the same operations repeatedly. Using hdparm (or bonnie) will give
> you lower bound for performance, which will be close to the real-life figure
> when performing an operation that isn't cached. Your approach will give you
> an upper bound, which should tend towards the bandwidth of your memory bus.
> 

I totally agree.  I not really going to reading 1 gig of data of the
disk most of the time I mess about with smaller files. I probably do
more reads than writes.

At the end of the day the dd test of reading 1 Gig did show performance
degradation on the inner portion of the device.

> > So how do I tell hdparm to test the inner or outer part of the device?
> 
> You can't, AFAICT. It always reads from the beginning of the block device
> you specify. This was why I had it report speeds for /dev/hde1 (in the fast
> zone) and /dev/hde9 (in the mid- to slow zone).
> 

Isn't that a limitation?

Tom.