On Tue, 17 Oct 2000, Larry McVoy wrote:
> On Tue, Oct 17, 2000 at 11:23:30AM +0200, Vojtech Pavlik wrote:
> > Well, I know quite well what this can bring us - with precise profiling
> > we could see the exact geometry of the drive
>
> LMbench has had something which does this for years. Look at
>
> http://www.bitmover.com/bw.gif
> http://www.bitmover.com/seek.gif
Great, but that was via a file system.
> The first shows you zone bandwidths, the second shows you a precise profile
> of the access times; you can get everything you might want from that.
> For example, the time quoted by all the drive people is 1/3 in from the
> left, at the bottom of the curve - a fairly misleading number if you ask
> me.
> Bingo. Screwing around with the elevator is in general a waste of time,
> but it is a rite of passage for all I/O people. I did it a long time
Well let me drown!
> ago and learned an important lesson: if your file system is good enough
> (and most are) there is almost nothing that can be done to improve
> performance - the file system has done all the work already. You're
> welcome to argue that point, but please do so with traces of a real
> system - not with your opinion. My opinion used to be the opposite
> and the traces moved me to this opinion.
Expand 'traces' ... O-SCOPE analyizer?
How can LMbench access things that I can but a FS can not?
Andre Hedrick
The Linux ATA/IDE guy
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