Re: [TCLUG:22248] Adaptec scsi performance

[Ben Kochie <ben@nerp.net>]

I don't know who told you this, but you are getting expected
numbers.  according to www.storage.ibm.com.
an 18ES (18.3gig 7200RPM) has the folowing specs:
susstained data rate of up to 20.2 MB/sec with a 7.0ms average seek time.
http://www.storage.ibm.com/hardsoft/diskdrdl/ultra/18esdata.htm

you have to remember, you are limited by media transfer rates, which
allways lag behind bus transfer rates, which is why i tell people that
even tho their UltraDMA/66 drive is fast, it's still no faster than what
can be skimed off the platters, and a 40MB Ultrawide chain will still
preform just as well. I did some benchmarks of the unloaded alpha 600, and
if i remember right.. I was geting over 33MB/sec out of a 10k RPM disk

Thank You,
        Ben Kochie (ben@nerp.net)

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On Thu, 5 Oct 2000, Michael Josephson wrote:

> On Thu, Oct 05, 2000 at 04:06:01PM -0500, Ben Kochie wrote:
> > yep.. that's about normal.. you are hitting DISK preformance limits.. not
> > chain limits.. here's what I get on a 10k RPM disk on an alpha 600 with a
> > symbios card.. you are also hitting the PCI bus limit of 133MB.  this is
> > an active box.. so the numbers are a little low :( (load is about 2 right
> > now)
> > 
> >  Timing buffered disk reads:  64 MB in  3.53 seconds = 18.13 MB/sec
> >  Timing buffer-cache reads:   128 MB in  3.06 seconds = 41.80 MB/sec
> > 
> > that's for normal UltraWide
> > 
> > this one is a K6-2 450, with a buslogic (mylex) scsi card, and a 7200 RPM
> > disk (i think) (backup server, no load)
> > 
> >  Timing buffered disk reads:  64 MB in  5.54 seconds = 11.55 MB/sec
> >  Timing buffer-cache reads:   128 MB in  3.28 seconds = 39.02 MB/sec
> > 
> > and finaly, a dual celeron with a 7200 RPM ide drive
> > 
> >  Timing buffered disk reads:  64 MB in  3.47 seconds = 18.44 MB/sec
> >  Timing buffer-cache reads:   128 MB in  1.49 seconds = 85.91 MB/sec
> > 
> > all drives are fairly recent (less than 1 year old) IBM ultrastars, and
> > IDE is a deskstar.
> > 
> > On Thu, 5 Oct 2000, Michael Josephson wrote:
> > 
> > > I'm running Debian (kernal 2.2.17) on a server at
> > > home: PIII 700 256MB ram with an Adaptec 29160 SCSI
> > > controller and an IBM ultra 160 hard drive. When I run
> > > hdparm -Tt /dev/sda, it reports:
> > > 
> > > Timing buffer-cache reads: ...= 128 MB/sec
> > > Timing buffered disk reads: ...= 19.05 MB/sec
> > > 
> > > I'm not expecting max performance, but 19 MB/sec is a
> > > helluva lot slower than 160 MB/sec. Anyone have any
> > > thoughts on this?
> ---end quoted text---
> 
> I've got a new IBM ultrastar 7200rpm (purchased in June). The box currently
> has no load. According to your numbers, I should be getting at least twice
> the 19MB/sec. 
> 
> I'm not too worried about this. But I'm trying to understand as much as I can
> about the hardware...I'm a programmer, not a doctor :-) I haven't noticed any
> performance issues, but the results of hdparm indicates to me that things could
> use some tuning.
> 
> mj
> -- 
>   Michael Josephson
>   Software Development/Web Administration
>   mjj@mjjtech.net
>   www.mjjtech.net  
> 
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