topic Re: Timing cached reads performance fall DL585 in Operating System - Linux

Timing cached reads performance fall DL585

Afanasiev — Sun, 15 Nov 2009 07:44:51 GMT

Die All,

I updating DB server from DL385 to new DL585, I have performance fall.
Tests show:

HP DL385
hdparm -T /dev/cciss/c0d0p1

/dev/cciss/c0d0p1:
Timing cached reads: 6426 MB in 2.00 seconds = 3215.23 MB/sec
HP DL585
hdparm -T /dev/cciss/c0d0p1

/dev/cciss/c0d0p1:
Timing cached reads: 1844 MB in 2.00 seconds = 922.00 MB/sec

RAID state id OK
hpacucli controller all show config

Smart Array P400 in Slot 9 (sn: PAFGL0P9SWY1MQ)

array A (SAS, Unused Space: 0 MB)

logicaldrive 1 (33.9 GB, RAID 1+0, OK)

physicaldrive 1I:1:1 (port 1I:box 1:bay 1, SAS, 36 GB, OK)
physicaldrive 1I:1:2 (port 1I:box 1:bay 2, SAS, 36 GB, OK)

I changed various BIOS settings, kernel settings and kernels, but it haven’t good effect.

What can I do to correct it? Thanks!

Re: Timing cached reads performance fall DL585

Vitaly Karasik_1 — Sun, 15 Nov 2009 12:18:11 GMT

Do you have the same type of disks (SAS) and the same RAID config in both cases?

Re: Timing cached reads performance fall DL585

Afanasiev — Sun, 15 Nov 2009 15:05:37 GMT

Yes, it's same disks

Re: Timing cached reads performance fall DL585

loco_vikide — Mon, 16 Nov 2009 22:31:44 GMT

You might want to compare the Read / Write Cache settings on your Raid controller (Model ???) on DL385 server and the SMart Array P400 controller on DL585 server

Cheers

Re: Timing cached reads performance fall DL585

Ragu_3 — Tue, 17 Nov 2009 00:58:24 GMT

For the array type you are using, assuming that the controller is supported for GNU/Linux, changing your scheduler type can help.

Re: Timing cached reads performance fall DL585

Mike Stroyan — Sat, 21 Nov 2009 02:49:59 GMT

The performance of "hdparm -T" is not really a function of the disk or disk controller.
It measures transfer time from the RAM cache.
It is a measure of the RAM read rate.
A decrease in the reported "hdparm -T" rate may point to a problem with installing DIMMS in a proper high performance arrangement
Or it might be a side effect of NUMA vs. SUMA memory arrangement which will differ between a DL385 and larger systems like a DL585. You could check DIMM arrangement with dmidecode and experiment with changing the BIOS SUMA/NUMA setting.