Dell SAS 5/i poor performance
This story begins about 3 months ago, when we have received first server from new Dell’s server line (PowerEdge 1950/2950). That server was a Dell PowerEdge 1950 with one Dual Core Xeon 5110 and two SATA drives connected to integrated controller. That server (in my mind) may be a good replacement for old PowerEdge 850 servers line. In a few weeks after first server delivered to our customer we have noticed about poor IO performance. I have made a few tests with bonnie++, and tests results was very terrible. There was about 30% difference in IO peformance between Dell 850, Dell 1950. Even my home PC with IDE drive was faster.First i have changed OS from FreeBSD 6.2 to Debian testing/unstable - results was same. Googling was a second step but there is not a lot of info about Dell 1950 performance. I have found only 2 posts on boards, but that posts was without replys. With all that info (bonnie test results and two posts on boards) i have write e-mail to Dell. In their reply they asked my to perform some tests with IOMeter using attached profile. Here is some info about test systems:
- “1950″
Dell 1950 / 1 Xeon 5110 / 1GB RAM / 2x 160Gb SATA300
Drives connected to integrated SAS 5 controller.
Drives vendor: Western Digital
Drives model: WDC WD1600JS-75N - “850″
Dell 850 / P4 2.8 / 1GB RAM / 2x 80GB SATA150
Drives connected to integrated ICH7 controller.
Drives vendor: Hitachi
Drives model: HDS728080PLA380
1950 was also tested with Seagate drives, but results not included below, because there is no difference in IO.
Test results you can find here
Basically, 1950 shows same or little better performance as 850, but only in sequential tests. Most of random tests shows what 850 is faster, and “Web Server” shows what 850 is MUCH faster.
After i have sent results to Dell they confirm problem in performance. From their words problem in LSI Logic chipset (LSISAS1068), that chipsend doesn’t have cache memory. So, if you need performance you need to buy PERC controller or Dell 850/860 servers line.
Conclusion: Newer != Better
April 13th, 2007 at 10:10 am
After spending weeks isolating, I came to the conclusion that
I/O is bad on 1950. But I need confirmation!
Googling awhile and you are my confirmation!!!
Thanks buddy.
April 13th, 2007 at 11:52 am
Call DELL support.
The Chap told me to try these setting:
And my I/O contention is gone!
“We need manually set ‘READ AHEAD’ & ‘WRITE BACK’
on your RAID CARD setting.”
My guess:
Last time, older DELL server RAID CARD have
hardware cache BUILT into the CARD but NEWER
server x290 series USES RAM instead of cache.
May 17th, 2007 at 4:41 pm
Same issue here 8-/
There’s a brand new firmware (april 17) to download from Dell’s website, I did not try it yet.
Did you set the “read ahead” and “write back” into BIOS (at boot time) or in your OS driver ?
May 23rd, 2007 at 4:40 pm
Klug, probably we are talking about different controllers.
SAS5/i even has not any BIOS
You are about PERC5/i and with PERC5/i we haven’t any problems.
June 12th, 2007 at 5:24 am
I have the *exact* same issue except I have a PE860.
Basically I’ve spent 2 days reading up about this issue and I have dell looking into it. I know I have to *enable* write-back cache but there is no place to enable it. Dell Open Manage does not give me the option, neither does the PERC5/iR Bios…
I’ve checked the LSI site - nothing
How do you enable write-back caching with this setup? I don’t care about power failure, I’m on UPS
Firmware Version 00.10.49.00.06.12.02.00
Driver Version 1.24.04.00
Windows 2003 DataCenter X64
dimitri_c at sympatico.ca
June 12th, 2007 at 5:31 am
Here’s some UNIX guys talking about the same issue:
http://www.nabble.com/Dell-SAS5-Performance-Issue-tf3474648.html#a9697855
Scott wrote me:
”
I added a feature to FreeBSD 6 and 7 last week that enables the SATA write cache on all drives directly connected to an MPT-SAS controller.
If you want to try this out, you’ll need to update your kernel sources and add the following line to /boot/loader.conf:
hw.mpt.enable_sata_wc=1
Most people are reporting a significant increase in write performance.
“
June 12th, 2007 at 1:15 pm
Dimitri, please note, PERC5/i != SAS 5i ;-)
I’m happy with my servers on PERC5/i, probably because almost servers has a lot of reads and no writes.
June 12th, 2007 at 1:16 pm
BTW, thanks for link
June 13th, 2007 at 5:16 am
fyi I fixed the issue today by enabling Write Caching on the VIRTUAL DISK via an older version of Dell’s Raid Manager found here:
http://www.dellcommunity.com/supportforums/board/message?board.id=pes_hardrive&thread.id=26011
My writes are much faster now but make sure you run your system on UPS if you go with this setup