Feedback solicited - read performance is awful with PE2650runningRH AS

Gary Mansell Gary.Mansell at ricardo.com
Tue Oct 28 05:17:00 CST 2003


Hi,

Thanks for your response - I cannot immediately see why your performance
should be OK when mine is problematic (I have tried this on two
identical PE2650's) This problem has also been seen on a HP system.

Perhaps you can have a look at the bug #106771 report on
http://bugzilla.redhat.com as I would be interested to hear if you can
think of any reason why I am seeing the problem but you are not.

Regards


On Tue, 2003-10-21 at 22:07, Wayde Nie wrote:
> Hi,
> 
> I've got a PE2650 running RHAS3b2. It has 4-36Gb disks in 2 HW mirror
> sets (presented as sda and sdb) on a PERC3Di (Adaptec aacraid driver).
> The box has 2x 2.4GHz Xeon's with HT enabled and 2Gb RAM.
> 
> The dd test results as follows:
> 
> [root at feweb tmp]# /usr/bin/time dd if=/dev/zero of=./testfile bs=16384
> count=250000
> 250000+0 records in
> 250000+0 records out
> 0.29user 47.06system 6:35.95elapsed 11%CPU (0avgtext+0avgdata
> 0maxresident)k
> 0inputs+0outputs (138major+15minor)pagefaults 0swaps
> ~10.34 Mb/s Write rate.
> 
> [root at feweb tmp]# /usr/bin/time dd if=./testfile of=/dev/null bs=16384
> 250000+0 records in
> 250000+0 records out
> 0.21user 17.91system 3:03.71elapsed 9%CPU (0avgtext+0avgdata
> 0maxresident)k
> 0inputs+0outputs (137major+18minor)pagefaults 0swaps
> [root at feweb tmp]#
> ~22.26 Mb/s Read rate.
> 
> > ----------------------------------------------------------------- <
> > Wayde Nie                                                         <
> > Software Analyst               Computing and Information Services <
> > phone: (905)525-9140 ext 23856 McMaster University, CANADA        <
> > fax:   (905)524-5288           niew at mcmaster.ca                   <
> > ----------------------[\]--->=\o.:---[\]------------------------- <
> 
> On Tue, 2003-10-21 at 07:17, Gary Mansell wrote:
> > I would really appreciate some help from the list here to see if anyone
> > else is suffering from the same problem that I am. I appear to have
> > fallen foul of a problem with RH AS products running on Dell PE2650's.
> > 
> > I have raised bug number #106771 at http://bugzilla.redhat.com and I
> > have tried to raise the issue with Dell but I am not getting very far -
> > both parties blame the other and I am stuck in the middle getting
> > nowhere.
> > 
> > I have installed RH AS 2.1 and RH AS 3.0b2 and have found that the read
> > performance from the system mirror is awful - it is less than the write
> > speed!! If I install RH 9.0 or RH 7.3 the read performance to this same
> > device is fine.
> > 
> > Please could anyone who has a Dell PE2650 with a version of RH AS
> > installed run the following quick and dirty (but representative) disk
> > performance tests and let me know if they find the same.
> > 
> > Write Performance:
> > /usr/bin/time dd if=/dev/zero of=/testfile bs=16384 count=250000
> > 
> > Read Performance:
> > /usr/bin/time dd if=/testfile of=/dev/null bs=16384
> > 
> > 
> > FYI, I have a Dell PE2650 with 2x 2.4GHz Zeons (Hyperthreading enabled),
> > 2GB RAM, 2x18GB internal system disks in a HW mirror configuration using
> > the Adaptec PERC 3Di.
-- 

Gary Mansell
Technical Computing Team Leader
IT Department

Ricardo Consulting Engineers Ltd.
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