I tested this on the standby (snapmirror destination) cluster - interesting findings (This is 8.1.2 7-mode on 3270 BTW) - 

pre-status (e1a is up and e1b is standby - I truncated the non-relevant stats for readability):

na04> ifgrp status
default: transmit 'IP Load balancing', Ifgrp Type 'multi_mode', fail 'log'
na04-vif0: 1 link, transmit 'none', Ifgrp Type 'single_mode' fail 'default'
Ifgrp Status Up Addr_set 
up:
e1a: state up, since 29May2013 11:19:37 (51+09:39:49)
mediatype: auto-10g_sr-fd-up
flags: enabled
down:
e1b: state down, since 29May2013 11:19:38 (51+09:39:48)
mediatype: auto-10g_sr-fd-up
flags: enabled

na04> ifgrp favor Fri Jul 19 21:00:00 PDT [na04:kern.uptime.filer:info]:   9:00pm up 51 days,  9:40 43403 NFS ops, 0 CIFS ops, 0 HTTP ops, 0 FCP ops, 0 iSCSI ops   
e1b
na04> Fri Jul 19 21:00:11 PDT [na04:kern.cli.cmd:debug]: Command line input: the command is 'ifgrp'. The full command line is 'ifgrp favor e1b'.


Check status (e1a AND e1b are BOTH UP - e1b "favored"):

na04> ifgrp status     
default: transmit 'IP Load balancing', Ifgrp Type 'multi_mode', fail 'log'
na04-vif0: 2 links, transmit 'none', Ifgrp Type 'single_mode' fail 'default'
Ifgrp Status Up Addr_set 
up:
e1b: state up, since 19Jul2013 21:00:11 (00:00:06)
mediatype: auto-10g_sr-fd-up
flags: enabled favored
e1a: state up, since 29May2013 11:19:37 (51+09:40:40)
mediatype: auto-10g_sr-fd-up
flags: enabled
na04> Fri Jul 19 21:00:42 PDT [na04:pvif.switchLink:warning]: na04-vif0: switching to e1b  
snapmirror status

42 seconds after the favor cmd the switch is made - e1b is now "down"

na04> ifgrp status
default: transmit 'IP Load balancing', Ifgrp Type 'multi_mode', fail 'log'
na04-vif0: 1 link, transmit 'none', Ifgrp Type 'single_mode' fail 'default'
Ifgrp Status Up Addr_set 
up:
e1b: state up, since 19Jul2013 21:00:11 (00:14:30)
mediatype: auto-10g_sr-fd-up
flags: enabled favored
down:
e1a: state down, since 19Jul2013 21:00:42 (00:13:59)
mediatype: auto-10g_sr-fd-up
flags: enabled

I repeated this test on the partner 3270 node - it took 31 seconds to report "switching to e1b"

What is happening during the transition?

From the commandline and snapmirror perspective this was non-disruptive (but there are no NFS clients running from the standby cluster) - a constant ping did not record any dropped packets or extra latency.

thanks to "Sto RageŠ <netbacker@gmail.com>" for reminding me I could at least test this on the standby cluster.






On Jul 19, 2013, at 9:53 AM, Fletcher Cocquyt <fcocquyt@stanford.edu> wrote:

Happy Friday

We're looking to make a change to the production cluster running 300 VM's including Oracle RAC ahead of the weekend full backups (which are bottlenecking on an edge HP switch - 1000 discards/sec at the peak on this 10Gb port)
So we want to run

 ifgrp favor <standby interface>

to balance the traffic out and avoid the discards

Do NFS clients (all our VMware datastores are presented via NFS vFilers) notice any issues when the standby interface (e1b) is favored over the active one (e1a)?

thanks

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