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Slow Raid 5 Write performance over network

Last response: in Storage
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November 8, 2007 7:46:53 PM

Hello!
I have a problem with my Raid 5.
The problem is that over the network the transfer rate is after a short while down to 1% from the normal 25-30%

From my desktop machine running windows XP I am moving a file to my Server. The transfer rate is in the beginning fast (I assume it´s the caching) but after a few seconds It becomes horrible slow.

Machines + Config
Server:
Core 2 Duo
2Gb Ram
Asus P5B Plus
4x Seagate 500Gb disks on Intel ICH8R in Raid 5
1x Sysdisk
Gbit Network Card on the PCI bus

XP Machine
Core 2 machine.
Gbit network

Ofc Gbit switch

Let me show you using pictures.



In this picture I move a file from my XP machine to the Raid 5 partition on my Win2k3 machine.
at first it´s fast then it becomes unbarebly slow.



On the second pic. It has gone about 5min or so when it goes fast again for a little while.


On the third pic. I am moving the same file to my sys disk. That goes at normal speed.


Internal, file moving is functioning good and no slowdowns like these are happening.


I havn´t found any solution or explanation for it beeing so slow. I have tried and disable write cache but it didn´t help.

Best regards
November 9, 2007 1:46:23 AM

Funny that you mention this.

I have the exact same issue myself on my home server, exactly as you describe it here. Similar, but not identical set up:

- Intel D945GNT motherboard, ICH7R south bridge.
- Onboard 1000Base-T Ethernet.
- Celeron D 2.8 GHz
- 1GB RAM
- 3Ware 9650SE RAID card, RAID-5, in a PCIx16 slot.
- Windows 2003 Server R2, SP2

I have run the performance monitor like you have, a telling metric to watch is the system free RAM. You'll see it go down quickly during the fast portion of the network file transfer as it buffers incoming data from the network. Then when the buffer runs out, that's when the network and disk write performance goes to schnike.

I don't have a solution, other than to say that what you're seeing is not an isolated incident. I've tried driver troubleshooting, write cache settings, PCI network cards, etc. Nothing has fixed the problem.

By comparing our two systems and eliminating all differences, we can discount the motherboard brand, RAID controller, processor, BIOS, memory, system drive, and probably drivers and settings. That doesn't leave too much except the Intel chipset.

I'm only speculating here, but I suspect the problem may lie in the Intel chipset - specifically the PCIe implementation on the north bridge (945G in my case, 965 in yours), or possibly something wrong with the south bridge chip (ICH7R in my case, ICH8R in yours). I think these desktop-level chipsets may not be able to properly handle high-speed data streams to/from multiple peripherals at a time.

I would be anxious to try a server chipset (Intel 3000/3010, 5000, etc.) under the same situation and see if the problem disappears.
November 9, 2007 2:44:37 AM

It would be nice to check if the problem occurs with the same setup with a Linux fileserver. I'm a windows guy but use Fedora 7 as a server OS. An install on another partition would test whether the SouthBridge is the culprit.

It could also be the switch/router causing the issue.

Jo
Related resources
November 9, 2007 5:26:29 AM

It Could be what you say that either Windows is handeling the raid badly or it´s a driver issue.
I dont see the switch beeing the problem as it has good speeds on transfers to the sysdrive.

Sam: Yeah, interesting to see other people with the same problem.
I am abit curious though. As chipsets with software raid support is becoming far more common, an issue like this would become evident really soon.
I am surprised that reviewers havn´t "found" out about this issue before.
November 9, 2007 6:47:27 AM

I wish chipset makers would have never put RAID-5 capability on their SATA controllers, so many people are fooled into thinking it's actually an acceptable setup.

If you want decent RAID-5, you need a good hardware controller, period. Performance (especially writes) on onboard will always suck horribly.
!