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Nexus 5548UP for SAN Switch

We have purchased a Nexus 5548UP switch for our SAN environment.  I've only configured it for jumbo frames and currently doing testing on the performance, as some say use jumbo frames while others say do not.  My question is, and I know this is a loaded question but how do you guys go about configuring your SAN switches?  What exactly are you configuring on it?  Such as for performance tuning or the like.  The reason I ask, is we have the switch and it's pretty much working, but I'd like to learn more about it and how to tune it and fully take advantage of the switch.

Reza Sharifi
Hall of Fame Expert

There is no need for performance tuning. Out of the box, the switches are capable of 10Gig line-rate speed.


Question for you Reza

I'm running iPerf with the following command iperf.exe -c <iperf server IP> -u -P 2 -i 1 -p 5001 -f m -b 15.0G -n 1000000000 -T 1 -w 128kb

I changed the window size little by little, but I started at 128kb.  The speeds didn't change much, but here's the results:

Transfer             Bandwidth
52.1 MBytes       437 Mbits/sec
52.1 MBytes       437 Mbits/sec
52.1 MBytes       437 Mbits/sec
53.0 MBytes       445 Mbits/sec
51.6 MBytes       433 Mbits/sec
52.1 MBytes       437 Mbits/sec


Even with overhead, that seems to be a little slow.  I was anticipating it being much faster on that switch.  Any ideas?  I've asked this question on another forum and nobody can provide me the reason why it's so slow, and I shouldn't say "so slow" as that's pretty fast but just expecting more for the 5548 switch.

So you are using iperf to transfer between 2 PCs/laptops?

I am not saying this is the case for sure, but it could be a limitation on how fast the PCs/laptops can read/wright.

Also what is the switch config for these tests?



That is correct, between two Dell Optiplex workstations.  We also tested between the server that will go into prod and an Optiplex, but once again the Optiplex could be the limiting factor.  You think that  could be it?  Here's my config, so you know how it's setup right now.



version 5.2(1)N1(7)
hostname N5K

feature telnet
feature lldp
feature vtp

username admin password 5 $1$oZ1234567898765432123456/  role network-admin

banner motd #Nexus 5000 Switch

ip domain-lookup
policy-map type network-qos jumbo
  class type network-qos class-default
    mtu 9216
system qos
  service-policy type network-qos jumbo
snmp-server user admin network-admin auth md5 0x422842c9d320064123456789fc703d20
 priv d3264f23456789000c703d20 localizedkey

vrf context management
port-profile default max-ports 512

interface Ethernet1/1
  flowcontrol receive on
  flowcontrol send on

interface Ethernet1/2

interface Ethernet1/3

interface Ethernet1/4

interface Ethernet1/5
  flowcontrol receive on
  flowcontrol send on

interface Ethernet1/6

interface Ethernet1/7

interface Ethernet1/8

interface Ethernet1/9
  flowcontrol receive on
  flowcontrol send on

interface Ethernet1/10

interface Ethernet1/11

interface Ethernet1/12

interface Ethernet1/13
  flowcontrol receive on
  flowcontrol send on

interface Ethernet1/14

interface Ethernet1/15

interface Ethernet1/16

interface Ethernet1/17

interface Ethernet1/18

interface Ethernet1/19

interface Ethernet1/20

interface Ethernet1/21

interface Ethernet1/22

interface Ethernet1/23

interface Ethernet1/24

interface Ethernet1/25

interface Ethernet1/26

interface Ethernet1/27

interface Ethernet1/28

interface Ethernet1/29

interface Ethernet1/30

interface Ethernet1/31

interface Ethernet1/32

interface mgmt0
  ip address
line console
  exec-timeout 720
line vty
boot kickstart bootflash:/n5000-uk9-kickstart.5.2.1.N1.7.bin
boot system bootflash:/n5000-uk9.5.2.1.N1.7.bin



Can you turn off

flowcontrol receive on
flowcontrol send on

and try again?

With both flowcontrol options off, I'm getting a consistent 525Mbit/sec throughput.

What exactly does the flowcontrol do?  That was recommended by another colleague to enable.

No need to have flow control on unless there are issues with pause frames from end devices i.e servers, VM, storage, etc..


Got it!  Good to know.


So in your opinion, are these speeds acceptable?  I know it also comes down to the 10GB NICs we are using.  We are currently using Intel X520 DA2 network adapters across the board.


Thanks for the advice and help, you are always so helpful on the forums Reza!


Glad to help and you are correct.  It depends on the NIC and also the PC/laptop.  I tested the same thing with 6500 1Gig interfaces and a couple of laptops with Gig NICs.  At about 600M, I could not move the mouse anymore and the laptop would freeze.

Please rate and mark the post as answered, so others can benefit from it.