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Mainframe Solutions

Fabric OS Firmware: The Intelligence Behind Switched FC Fabrics

by Dave Lytle ‎12-06-2013 02:27 PM - edited ‎12-06-2013 02:40 PM (16,506 Views)

If one considers a switching chassis to be the body of that device then the central processing unit (CPU) is the brain and the firmware code is the intelligence residing within that brain on that machine.  So it is the firmware that issues requests out to the rest of the “body” and then monitors and reacts to all of the sensory information coming back in to it.  Each Brocade switch type, contained within a Fibre Channel (FC) storage networking fabric, must have an appropriate release of firmware intelligence in order to run all of the features and functions of the switch.  Brocade’s intelligent firmware is called Fabric Operating System or Fabric OS or more commonly just FOS.  FOS is a very mature (16+ years), highly capable software system used to control the features and functions of all the Brocade FC SAN products that we produce.  It is how we deliver savings, choice and solutions to customers across multiple generations of products.  In a nutshell, FOS helps a switch do what it is supposed to do.


Brocade FOS firmware is the Operating System that boots up and executes on our Fibre Channel switching products and it is used with the same intent that you have for the operating system running on your laptop or desktop or server – to deliver the unique operating environment which provides the functionality desired by the user of that device.  FOS will configure, control and monitor the functions that are available across the various hardware components housed within a Brocade FC switch.  FOS runs on the entire Brocade family of FCP and FICON backbones (Directors) and switches providing transparent interoperability between 1, 2, 4, 8, and 16 Gbps devices.


Brocade FOS is a collection of switching, routing, internetworking, monitoring and other functions that have been synergistically integrated into a multi-tasking operating system that provides each of our FC switching products with its basic and advanced functionality.  FOS has evolved into a very powerful system that controls and monitors the many different functions available within the hardware platform where it resides: low-level hardware controls (think “drivers”); services that control behaviors and retain information; embedded management interfaces to support “direct” switch management (think CLI); as well as external switch management (think SNMP).


Over time as technology evolves, hardware switching products come and go, but their software control systems remain.  Brocade understands that most customers are initially attracted to our superb hardware products and their features and functionality.  However, over time, it is often FOS and our Brocade Network Advisor management software, delivering an ergonomic interface look and feel as well as exceptional performance and high availability, that usually keeps our users coming back for upgrades and technology refreshes.  And FOS is intentionally designed as a platform that can deliver long-term investment protection as enterprises grow, scale and refresh their environment in the fullness of time.  Central to our investment protection strategy for customers is our growing number of optional licensed features and capabilities.  Users can easily select and deploy any licensed features that will benefit their enterprise such as Inter-Chassis links, 10 Gbps links, FICON Control Unit Port (CUP), FICON performance acceleration over distance and many others.


As you can imagine, FOS code changes and evolves with each generation of FC switching that is released.  As new generations of FC switching devices are released, a newer, updated FOS release of software will have evolved and been qualified to operate those devices as well as the directly preceding device generation.  That is why FOS 4.x was deployed to handle 2 Gbps FC SAN devices.  That was followed by FOS 5.x for 2 Gbps and 4 Gbps products; FOS 6.x for 4 Gbps and 8 Gbps products (occasionally but unofficially referred to as Gen 4) and currently FOS 7.x for 8 Gbps and 16 Gbps products (now rebranded as Gen 5).


The figure 1 attachment to this blog, is a graphic representation of how Fabric OS can be deployed on its designed environment or the immediately preceding environment.


As you can see in figure 1, each major release of FOS code has the ability to control the prior generation of FC SAN devices as well as to control its design point generation of FC SAN devices.  But even during the life of a FC switching product, the FOS platform is continually evolving new and better capabilities.  During its life cycle a FOS release might have several major upgrades and a number of minor upgrades.  A FOS “Version” is the full number/letter combo (X.Y.Zx) such as 7.1.0c.  The X is the platform level where a “7” is known to support current Gen 5 (16 Gbps) as well as previous 8 Gbps platforms.  Y is a feature (typically major) release level.  Z is maintenance release level.  And “x” is the patch release level.


It is important to point out that even though a FOS version is supported for FCP it might not be supported for FICON.  Working with Brocade, IBM does significant additional testing against a FOS set of code before it will release a FOS qualification letter in support of System z environments.  Users will find that only very specific versions of FOS code are acceptable to be used in System z environments which means that your switching devices in these environments must be running a FICON qualified and supported release of FOS code.  You can find the FOS releases that are supported by IBM in System z fabrics at:

When you access this page go to the MAINFRAME section.


Users can also access the FOS release notes that are relevant to a specific FOS release.  Use the website and in the upper right corner click on” MyBrocade Log in”.  If you have not already done so, please register (no fee) using your company email ID and provide a password that will be used for your future log ins.  This will allow you to access many technical documents and user communities.


On the Welcome To MyBrocade page:

  • Click on “Downloads” that is highlighted about midway down the page.
  • When the Downloads page appears, choose Download By “SAN Directors” under Product Downloads.
  • At the top of the Product Name area you will find “Fabric Operating System (FOS)”.
  • Click on the arrow mark to open this section.
  • It might take a few moments to show its documents so be patient.
  • The latest FOS releases are shown at the top of this section.
  • Click the arrow mark on the version of FOS or FOS manuals to which you would like to have access.
  • Look through the section to find the specific Release Notes that you desire to view.
  • It will give you an option to OPEN or SAVE the file.
  • There is often a FICON Enhancements section in the Release Notes document so do not overlook that important information.
  • But specific to this blog, the Release Notes will provide detail about which existing and which new products are supported by a given release of the Fabric Operating System.

Brocade has a good process (Target Path) for keeping our OEMs and partners synchronized on FOS code levels for interoperability within FCP and FICON environments.  But mainframe FICON environments are different, very conservative, really more of a subset of the FC protocol that has purposely limited capability in order to increase robustness and high availability characteristics.  This differentiation makes a mainframe environment more problematical when it comes to finding a single FOS release that is acceptable for interoperable usage between the IBM mainframe and each of the other storage vendors in switched-FICON, System z environments.  Based on each OEM’s qualification schedule, launch schedule, particular requirements for behavior with their storage products and other factors, it is difficult to get complete alignment – in terms of timing and specific patch code level - for a brand new major FOS release across all OEMs.  And that is where Target Path comes in which gives us our best chance of getting all OEMs supporting the same version of code.


Users should be aware that Brocade has not in the past and currently does not provide a comprehensive partner matrix of FICON supported FOS releases and general availability (GA) dates.  The reason for that is each OEM partner’s desire to manage the relay of this information to their own customers.  Each of our partners can test, certify and release mainframe-oriented, Brocade FOS code based upon their own internal requirements.  This often means that a FICON approved FOS version from Brocade will be released and supported on different GA dates by each of the storage vendors.  So users must go to the websites hosted by each of their storage vendors, or directly to the storage vendor, to find FICON related FOS version information and then correlate it for their enterprise so that a proper, qualified and supported FOS version of code for FICON, across all of the connected vendors, is deployed.


Below are some links that a customer can utilize to determine each storage vendor’s FICON supported FOS releases.  Of importance to note, in any switch-based Fibre Channel environment it is a best practice to try to run all of the switches in all of the fabrics on the same FOS release level of code if possible.  This is especially important when deploying FICON cascaded fabrics.



  • Login or create a new account at this site (no fee) if necessary.
  • Choose SUPPORT from the menu bar.
  • Cursor over “Interoperability and Product Lifecycle Information”.
  • Cursor over “E-Lab Interoperability Navigator” and click on it.
  • In the body of the message click on “Launch E-Lab Interoperability Navigator”.
  • It might take a little while for this site to resolve itself.  Be patient.
  • Under CONNECTIVITY click on SWITCH.
  • Find BROCADE as a switch vendor and then find your specific switch product.
  • Click on that selected switch (and you might have to do this several times if several different switches are deployed in your enterprise).
  • Firmware levels will be displayed and a FICON notation will alert you to the most current System z qualified FOS release.
  • Unfortunately, this site does not tell you about ALL of the supported FICON releases.  For example, it might show that FOS v7.0.0c is supported for FICON.  But it does not tell you that FOS v6.4.2a is also supported for FICON.
  • Do not hesitate to contact your local EMC SE or support person to provide additional information.


  • You can find the hyperlink for “USP V and USP VM FICON Switch support” but this is inclusive of FOS 6.x only and does not provide any information about FOS 7.x or above.
  • Information about the FOS required to support the Virtual Storage Platform (VSP) is not provided.
  • Unfortunately, the FICON FOS information that users would really like to access is not currently reported on this website.
  • My information suggests that HDS views this as confidential information and only distributes that information internally and not directly to their users.
  • HDS has a Tech Tip email that they send out to notify internal pre-sales SE and support recipients of the supported FOS versions, by switch type, for FCP, True Copy/HUR, and FICON.
  • At this time a user’s best option is to contact their local HDS SE and ask them to share the FICON FOS levels that are currently supported in mainframe FICON environments.
  • A basic rule-of-thumb is that HDS always follows a bit behind the IBM FICON Qualification letter for supported FOS versions, equipment models and releases.  Usually there is a 2-6 week delay after the IBM FICON Qualification letter is released which allows HDS to do their own testing and certification process.  Experience suggests that typically the HDS internal qualification is completed within 4 weeks of the IBM FICON Qualification GA for a FICON FOS version of code.


  • If the user has purchased the FICON switch from Oracle then they will have access to MOS (My Oracle Support).  There they are able to access the latest switch FOS versions that are supported by Oracle.
  • At this time they do not have a publicly viewable website.
  • A user’s best option is to contact their local Oracle SE and ask them to share the FICON FOS levels that are currently supported in mainframe FICON environments.




Interoperability within a storage network today is commonplace, since no single vendor provides switches, storage nodes, and connectivity adapters.  In fact, the majority of mainframe storage networks have multiple storage vendors (a DASD vendor and a tape vendor, or two different DASD vendors, for example).  Moreover, storage network device interoperability is well understood: SAN vendors provide interoperability matrices and have extensive experience designing, implementing, managing, and troubleshooting heterogeneous storage networks.


As presented here, Brocade’s Fabric OS is the operating system firmware that provides the intelligence for the CPU brains under the switch covers for deploying robust storage networks and in particular, mainframe storage networks.  FOS runs on the Brocade family of Fibre Channel and FICON Directors and switches—providing transparent interoperability between 1, 2, 4, 8, and 16 Gbps devices for superior investment protection.


All of the functionality of FOS is resident in the FOS version of code that is deployed on a FC switching device.  Some of that FOS functionality must be enabled through standard licenses such as the Enterprise Bundle licenses, or through the optional licenses such as the FICON Management Server (CUP) license.  But no new FOS code is ever added to a switching device just because a license is enabled on that device.  All of that FOS code is already there – it is just not being used until the license allows it to be used.


Brocade FOS also enables the reliable, high-performance data transport that is crucial for interconnecting thousands of servers and storage devices within a fabric.  And it delivers industry-leading technologies that help improve performance, efficiency, RAS, and optimization of those SAN fabrics at an affordable cost.  The integration of our innovative Brocade FOS with FC SAN fabric technology uniquely enables Brocade products to provide the building blocks that solve today's challenges and act as a strategic foundation for next-generation data centers.

on ‎12-10-2013 10:21 AM

Great write up Mr. Lytle!

by Martin Mune
on ‎01-22-2014 10:51 AM

Awesome job Mr. Lytle!  Very useful!

by pacatala
on ‎02-25-2015 06:48 AM

Just to add, you can find the IBM z Systems Qualification Letters at IBM's Resource Link website.


If you have never been to Resource link before, please create an IBM ID and then request access. The website is publically viewable after registeration and access request has been granted.


~PJ Catalano, IBM Vendor Solution Connetivity (VSC) Lab's Team Leader