Flowcontrol - Throughput issues

Brendan Marmont · ‎08-13-2013

This is one example, I have a NAS 10GbE connected to a 4507 10GbE interface. When I copy a large CIFS file, the resource reports are telling us we are getting 20-30MBs, OS tells us 7MBs? Apart from the obvious reported throughput differences, thats slow!

Devices IPs are in the same subnet, Interface config

interface TenGigabitEthernet5/10

description QNAP 10GbE

switchport access vlan 10

switchport mode access

spanning-tree portfast

I'm not so familiar with flowcontrol (Just yet ) could this be affecting our system throughput negatively? The show flowcontrol output is not consistant, I have listed the 10GbE line cards stats below.

Some explanation as to why some Flowcontrol operations are 'on' 'off' 'disagree' and why Recieve Admin is set to 'desired' and 'on' - is this automatically generated by the system, I certainly did not specify these configurations.

Port Send FlowControl Receive FlowControl RxPause TxPause

admin oper admin oper

--------- -------- -------- -------- -------- ------- -------

Te5/1 on on desired on 325168 3773725

Te5/2 on on desired on 166494 3847509

Te5/3 on on on on 43476 65887

Te5/4 on on on on 489200 1649744

Te5/5 on on desired on 595828 1607934

Te5/6 on on on on 11910638 6504

Te5/7 on off on off 1974 26

Te5/8 on off desired off 14 0

Te5/9 on off on off 4470 4

Te5/10 on on on on 25704 0

Te5/11 on off desired off 0 0

Te5/12 on on desired on 11915312 0

Thanks in advance

Brendan

Reza Sharifi · ‎08-13-2013

It is common to have jumbo frames enabled on the device where storage connect to. Is jumbo frame enabled?

HTH

Brendan Marmont · ‎08-13-2013

I've tried a MTU 9000 and the throughput still performs like a 10MB link.

Thanks

Joseph W. Doherty · ‎08-14-2013

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This is one example, I have a NAS 10GbE connected to a 4507 10GbE interface. When I copy a large CIFS file, the resource reports are telling us we are getting 20-30MBs, OS tells us 7MBs? Apart from the obvious reported throughput differences, thats slow!

Are both your resource reports and OS measuring in bits per second or bytes per second? Networks often report in the former and OSs in the later. Also, sometimes network stuff also accounts for bandwidth being used by L2, often OSs do not.

With CIFS, older versions of SMB weren't too optimal for high speed links. Additionally, if running over TCP, older Windows devices (pre-NextGen) didn't allocate very large TCP RWINs. However, from your very low rate, which is lower than I would expect even with older SMB and/or pre-NextGen TCP, your NAS is 10g, but what about the host? I'm wondering whether you NAS sends bursts that are being dropped if bandwidth to the host is less than 10g. If your NAS keeps cycling through slow start - that might account for your slow overall transmission rate.

Of course, there are many other possible issues to. For example, your (?) 4712 line card is, by design, oversubscribed 2.5:1.

BTW, "ordinary" Ethernet flow-control often "hurts" performance.