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8531
January 31st, 2006 04:00
Jumbo frames... am I missing something?
I have recently moved my servers to an all gigabit ethernet network and I'd like to make use of jumbo frames. They're enabled on the switch (PC 5324) and I changed the default MTU to 9000 (up from 1500) as someone on a mailing list said to do that.
However, the performance is horrible... and maybe I am missing something. The cabling should all be fine, it's brand new cat5e.
Here's my test with 3 servers at the moment:
A has jumbo frames (mtu 9000)
B has jumbo frames (mtu 9000)
C has normal (mtu 1500)
B -> A = 3.4MB/sec
C -> A = around 50MB/sec
I'm just scp'ing a 170 meg video file back and forth - it's over 10 times slower... does anything stand out to you instantly as to what the problem would be?
All the servers are identical config:
* Dual-core Opteron 175
* 2x1 gig DDR3200 ECC
* Seagate 250G SATA
* Serverworks HT1000 chipset on a Supermicro H8SSL-i motherboard
(specs: http://www.supermicro.com/Aplus/motherboard/Opteron/HT1000/H8SSL-i.cfm)
* appears to be Dual-port Broadcom BCM5704C Gigabit LAN / Ethernet Controller
* Debian-amd64 Linux kernel 2.6.15.1
Thanks in advance for any help or suggestions!
However, the performance is horrible... and maybe I am missing something. The cabling should all be fine, it's brand new cat5e.
Here's my test with 3 servers at the moment:
A has jumbo frames (mtu 9000)
B has jumbo frames (mtu 9000)
C has normal (mtu 1500)
B -> A = 3.4MB/sec
C -> A = around 50MB/sec
I'm just scp'ing a 170 meg video file back and forth - it's over 10 times slower... does anything stand out to you instantly as to what the problem would be?
All the servers are identical config:
* Dual-core Opteron 175
* 2x1 gig DDR3200 ECC
* Seagate 250G SATA
* Serverworks HT1000 chipset on a Supermicro H8SSL-i motherboard
(specs: http://www.supermicro.com/Aplus/motherboard/Opteron/HT1000/H8SSL-i.cfm)
* appears to be Dual-port Broadcom BCM5704C Gigabit LAN / Ethernet Controller
* Debian-amd64 Linux kernel 2.6.15.1
Thanks in advance for any help or suggestions!
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DELL-Cuong N.
1K Posts
0
January 31st, 2006 18:00
It maybe that it has nothing to do with the switch. Jumbo frame is not always worthwhile if the application you are running doesn't utilize it and sometime may result in more problems.
One thing you might try is to enable "flow control" on the switch to see if it will help. If the sender is sending too fast and the receiver is not able to handle the incoming flood, it may drop the incoming packets resulting in alot of retries which will certainly degrade your performance. So pushing alot of traffic through a large pipe but with the end points not being able to handle the load may result in worse performance.
You could also try reducing the packet size and playing with the settings until you find the optimal setting that give you the best performance.
Cuong.