Enabled Jumbo Frames but now I have High Total Outqueue Drops

[criitdept]

Hi,

I hope someone can help me with this.

I have enabled Jumbo Frames in our iSCSI Network to hopefully help speed things up (I really wanted to use more of the available bandwidth as have gigabit nics which are only be utilised by 5-10%)

This consists of....

• 3 Meshed (etherchanneled) Catalyst 3560-x Switches with System MTU Jumbo set at 9000
• 3 HP p4300 G2 SAN's split across across the switches using ALB with the MTU set at 9000
• 2 HP DL380 G6 File Servers split across the switches using teaming with the NIC's Jumbo Packets set as 9014 (the only Jumbo Option)

These are the only servers connected to these switches so i have ensured that everything is configured for Jumbo Frames.

Since I have made this change, the network hasn't improved and is maybe a little slower.

I have checked the interfaces on the cisco switches that these are plugged into and these interfaces all have quite a high amount of Total Outqueue Drops.

To hopefully get round this, I enabled flow control and I still have the same problems

Can someone please help me troubleshoot this or help me get the most of my network.

Thank you so much

James

[smehrnia]

Hi,

you might need to tune your buffers.

plz Rate if it helped,

Soroush.

[criitdept]

Hi Soroush,

Thanks for the quick response.

As I'm pretty new to doing this, can you explain how to do this and a correct benchmarck for these.

Thanks again,

[smehrnia]

Hi,

if qos is not already implemented and since we dont want to implement a complex QoS at this point, try this n see if it solves your problem.

Switch#config term

Switch(config)#mls qos

Switch(config)#mls qos queue-set output 1 threshold 1 1000 1000 50 1000

Switch(config)#mls qos queue-set output 1 threshold 2 1000 1000 50 1000

Switch(config)#mls qos queue-set output 1 threshold 3 1000 1000 50 1000

Switch(config)#mls qos queue-set output 1 threshold 4 1000 1000 50 1000

plz Rate if it helped,

Soroush.

[criitdept]

Hi Soroush,

Thanks for the config.

I have tried it but unfortunately, it doesn't seem to have helped.

Do i need to then apply this to particular interfaces?

Thanks

James

[smehrnia]

No it is global, just enlarged the output queue drop thresholds for queue-set 1.

check this Link, find out if your links are using queue-set 1 or 2. if they are using 2, this config should be applied on 2 too.

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a0080883f9e.shtml

here also you can read about buffer size for egress queues.

Hope it does help!

plz Rate if it helped,

Soroush.