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How Do I…Know When Virtual Fabrics Are Required For FICON Deployments?

by ‎04-30-2014 02:56 PM - edited ‎04-30-2014 03:24 PM (3,105 Views)

Looking back to the beginning days of when our careers began here at Brocade, I asked my colleague Martin Mune (who began on the same day as I did back in 2006), what made him the most nervous as we were learning product, features and Brocade technology.  Here's what he had to say...


Martin Mune:  "When I first started at Brocade too many years ago to comfortably admit now, the mention of 'FICON' or 'Mainframe' was enough to make me 'shake in my shoes. That is to say I found the whole other set of terms scary and confusing. However, thanks to the very patient teachings of some of the smartest folks I’ve had the pleasure to work with, I finally got to the point where the shaking stopped, the fear subsided, and the confusion went down to my normal level. So, when Virtual Fabrics came along, I thought I might be in for another 'shoe quake'. I thought the addition of Virtual Fabrics is only going to complicate matters."


So in looking into this sceanrio, who better to speak to it then a FICON/Mainframe expert... enter our own Dave Lytle (a Brocade Global Solutions Architect).  Dave provided a detailed answer on the topic of Virtual Fabrics and when to deploy in FICON environments.


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Dave Lytle:  "It boils down to the port count. In short, Virtual Fabrics is only mandatory on the DCX 8510-8 (IBM: SAN768-B2) when 48-port connectivity blades (FC16-48 and/or FC8-48E) are used in the chassis. That is due to the fact that z/OS can only count up to 256 (00-FF). Since the DCX8510-8 chassis with eight 48-port blades would provide a total of 384 ports of connectivity and z/OS cannot handle any domain that contains more than 256 addresses, we must use Virtual Fabrics to create smaller sets of addresses. 32-port blades (FC16-32 and/or FC8-32E) in all 8 slots of a DCX8510-8 (IBM: SAN768-B2) would be exactly 256 addresses in a domain which would be a perfect fit for z/OS. So, if one has only 32-port blades or even a couple of FX8-24 extension blades, then the use of virtual fabrics does become optional.


It should be noted that enabling VF on a chassis is an offline procedure so it is recommend to enable VF even if you don't 'need' to have multiple Logical Switches at the time. Once VF is enabled VF, a Default Switch (domain id 128) will be created and all of the ports will be hosted (or “located”) there. If  you have more than 256 ports, then you’ll need to create one or more Logical Switches and then 'move' the ports out from the Default Switch to your created Logical Switches. Lastly, if you should enable VF and create Logical Switches, you could consider keeping any un-cabled, unused ports in the Default Switch until those ports become needed. This can add extra protection for the infrastructure from connectivity 'errors' by isolating those 'extra' ports."


Thats it!  We'd like to thank you Dave, for not just your input but allowing us to write this up.



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