Tuesday, July 15, 2014

Network Outage? What Network Outage? Nimble Seamless Network Failover

Hi Friends,

A co-worker of mine is a data protection wizard and he was looking at our array and asked what would happen if the management network went down on the active controller?  Hmmm, good question....  Networks are so darn stable these days we don't really even worry about management networks anymore.  Back in the good old days you had to worry about autonegotiate, hard coding, mis-match collisions, you name it!  But these days, stuff is so stable, sometimes we don't even plug in the redundant management cable because we don't need to worry about it.

But, what about the unknown factor, like people.  I've said it before that people are chaotic, unpredictable, and generally abusive to hardware.  So what happens if the management port goes down?  Well, data keeps flowing because those are on the 10gig iSCSI lines, but administration, calls to backup programs, and generally anything that happens outside of the array just won't work.  Is it mission critical, probably not, but it can certainly ruin your day.

So my friend decided to try out a test.  He added two more management cables, one to each controller, to see how easy it is to configure and if link failure was disruptive or not.  So how hard is it to configure in the Nimble?  SIMPLE!  Yeah, so easy even **I** can do it!  You plug in the secondary NIC and set it to management in the GUI.  That's it!  Now of course you can get fancy, but he put it on the same subnet because that's what is the easiest and 9 times out of 10 its what you'll probably want to do.  In the past if you wanted redundancy you had to do some sort of NIC teaming or put stuff on multiple subnets or networks and it might not be automatic, the list goes on.

So how easy is it?  Well, take a look at the GUI.  You go into Interfaces for eth2 and literally just select Management!  NO, NO, NO, NO, NO!  It can't be that easy!!

Well, let's try a test.  Let's pull eth1 and see what happens...

Yep, eth1 is down...  and...  so...  In your face skeptics!!  :-)  We keep happily running eth2, no loss of connectivity, no problems.  Okay, I know what you're thinking, what happens if both NICs go out on that controller.  I like the way you think!  Let's pull eth2 and find out.

Still NO down time, OH YEAH!  Both NICs are down and we've failed over to Controller B.  Remember, Nimble runs Active/Standby, so switching over doesn't cause downtime.

So even if you accidentally pull the wrong network cord, like that would ever happen, we've got your back!

Special thanks to Bill Roth for thinking of and testing this scenario!

Until Next Time!

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