Feedback solicited - read performance is awful with PE2650runningRH AS

Keith Schincke kschin at
Tue Oct 28 09:16:01 CST 2003

My system does not run AS but here are my numbers.

Here are my times:
Write:  4:18 (~15.8)
Read: 1:44 (~39.3)

My system spec's are PE2650, 2x2.4 hyperthread enabled, 2Gb, Perc3DC to 
a RAID4 PV220. The server is running RH9 with a stock 2.4.20 
kernel with LVM1 and XFS patches for that version. The system has been 
pretty stable and will have an 80day uptime by the end of the day (I hope).


Gary Mansell wrote:
> 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
> 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:
>>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
>>250000+0 records in
>>250000+0 records out
>>0.29user 47.06system 6:35.95elapsed 11%CPU (0avgtext+0avgdata
>>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
>>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                   <
>>>----------------------[\]--->=\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 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
>>>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.

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