Virtual Connect (VC) SAN login question

[chuckk281]

Vjith had a FC SAN login question:

**************

How can we check fabric logins are distributed across virtual connect flex fabric module?

Manual or Automatic login distribution, which is recommended?

**********

Reply from Dan:

***********

First Question:

Go into VC Manager \ Connections \ SAN Fabrics

Then on the main window go into the Server Connections Tab.

There is a column there that will tell you for each SAN Login which Uplink Port was used.

Second Question: I don’t have a recommendation, I explain both to the customer and let them decide.

There  is no major difference between Auto and Manual unless you have an Uplink Failure or you add Uplinks.

If you have a transceiver or cable go bad on you, and you lose 1 of 4 uplinks let’s say.

Then the servers on that uplink get moved to other uplinks immediately and automatically via a request to login to the fabric again.

Auto vs Manual only matters when you Add new Uplinks or replace that failed one.

When you do either, there are Zero connections on that new/replaced Uplink to start with.

Manual = You need to go to the SAN Fabrics screen, right click on the Fabric in question and select Redistribute Logins.

Automatic = Every X seconds, the system will check to see if the logins are balanced (not load, it just looks at logins) and will move some connections around if it finds they are not.  The timer is set under Domain Settings \ Fibre Channel \WWN Settings \ Misc. Tab

Manual = You have more control of when that new/replaced uplink gets put into service.

Automatic = Within X seconds of the connection being verified as online, some servers will have 1 of their 2 FC ports logged out of the fabric and then back in on the new connection causing a minor blip on that FC port of the CNA/HBA.  Not all servers, only enough to cause things to be balanced will be affected.  But you have zero control over which those are.

If you left it in Manual, and you forgot to Rebalance the logins, then anytime a server was rebooted (or crashed and rebooted), as it boots back up, the FC Login will happen and VC will place it on the least used uplink, including those new/repaired ones.

***********

Other comments?