> -----Original Message-----
> From: Corin Hartland-Swann [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, July 27, 2000 7:15 AM
> To: Holger Kiehl
> Cc: [EMAIL PROTECTED]
> Subject: Re: Question on disk benchmark and fragmentation
>
> Holger,
>
> On Thu, 27 Jul 2000, Holger Kiehl wrote:
> > Will this not influence the performance a lot since the head of
> > the disk has to walk all over the disk? Thus making comparisons
> > practically useless since you never know the state of fragmentation?
>
> I think you've got it exactly right here. Whenever I do a
> benchmark on a
> disk, I follow the following basic plan:
>
> 1) Use a freshly formatted disk
> 2) Disable all but 32M RAM
> 3) Switch to single-user mode
> 4) Measure performance at start (maximum) and end (minimum)
> 5) On large disks (>20G or so), try the first 1G and the last
> 1G by using
> fdisk to create partitions there
> 6) Use tiotest, NOT bonnie! Try multiple threads (I use 1, 2,
> 4, 8, 16,
> 32, 64, 128, 256 threads - this is perhaps excessive!)
What size datasets are you using? Bonnie++ is still a good benchmark,
although it stresses things differently. The maximum number of threads that
you should need to (or probably even want to) run is between 2x and 3x the
number of disks that you have installed. That should ensure that every
drive is pulling 1 piece of data, and that there is another thread that is
waiting for data while that one is being retrieved.
> > Hope this is not to much off topic.
>
> I think it's pretty important when talking about RAID, since
> a lot of us
> are using it for performance reasons, with the redundancy as an added
> bonus.
Heh, I'm using it because it provides redundancy, the added speed from
Mika's RAID 1 read balancing patch is just a perk... HTH,
Grego
