In DB2 for z/OS circles, there has been an evolution of attitudes concerning Linux on System z. Back around 2003, when I was on the user side of the DB2 community, I was part of a team charged with developing a plan for the simplification and streamlining of my company's IT infrastructure. One of the mainframers on this team had a suggestion: why not add a few IFL engines (more on this to come) to our System z servers and use those to consolidate a lot of our Linux systems (which were running primarily on x86 boxes)? I'll confess that this suggestion seemed a little weird to me, a little "out there" -- Linux on a mainframe? Really? The person who was advocating running Linux on System z made some good points, but the idea didn't get far and was set aside. Linux was kind of new to us at the time, and while we were ready to increase the use of this OS in our environment (and we did), we weren't ready to even seriously consider running it on mainframes.
Fast forward to 2010. A few months after rejoining IBM (I'd previously worked for Big Blue from 1982 to 2000), I was working with people at an insurance company where Linux on System z was being put through a trial run. What they were willing to run under Linux on System z was a DB2 Connect gateway, not a more high-profile workload such as an application server or a business analytics tool -- an indication of the iffiness of the Linux-on-z solution as seen by the firm's IT leaders.
Jump now to the present, and it seems to me that a corner has been turned. Over the past couple of years especially, the thinking of many IT people -- both mainframers and Linux specialists -- towards Linux on System has gone from cautious consideration to genuine enthusiasm. All kinds of folks have recently come to the realization that Linux on a mainframe is not some kind of sideways, six-of-one/half-dozen-of-the-other move, in terms of where Linux runs in the enterprise; rather, it's a move that upgrades the IT infrastructure in multiple ways, delivering enhanced performance, cost efficiency, availability, and security. A big chunk of installed System z MIPS, right now, is IFL capacity, and that slice of the pie is growing at a rapid clip (IFLs -- short for Integrated Facility for Linux -- are System z processors that are dedicated to Linux workloads). If I were you, I'd be looking to ride that wave.
In terms of factors that are driving the upsurge in Linux on System z usage, two really stand out: server consolidation and front-ending DB2 for z/OS. That first factor applies to Linux systems that may or may not have any connection to DB2 for z/OS subsystems. A wide variety of Linux workloads can be more cost-effectively run on mainframes versus distributed systems servers. Want to know what one of the big money savers is here? Think software licensing costs: the price of commercial software that runs under Linux is usually based on the number of processors on the system (or the partition) on which the OS is running, and plenty of organizations have found that moving Linux workloads to mainframes results in a decreases in the number of engines needed for those workloads, and that allows for a reduction in licensing costs for vendor-supplied software running in the Linux images.
That reduced-cost advantage also comes into play with regard to the second Linux-on-z driver, DB2 for z/OS front-ending. So do advantages in the areas of performance and security. When a Linux workload -- perhaps an application server running Java programs, or a vendor-supplied ERP or CRM package, or a business analytics tool -- is the client to a DB2 for z/OS server (i.e., if the Linux-based application is a DB2 DRDA requester), that back-and-forth network traffic can flow via HiperSockets. That's memory-to-memory data transfer, folks, and it screams. This "internal LAN" set-up also offers a security benefit, as less of your network is physically exposed to those who might want hack it (as Jim Elliott, one of IBM's prominent Linux-on-z experts, likes to put it, "The best LAN is one with no wires").
At this point, I would be remiss if I didn't bring z/VM into the picture. Can you run Linux on System z without z/VM? Absolutely, but z/VM delivers tremendous virtualization, management, availability, and security capabilities for your Linux-on-z environment. On the security front, RACF for z/VM brings the same peerless validation and auditing features that have made RACF for z/OS famous (note, too, that the cryptographic hardware on System z servers can be exploited for Linux workloads). High availability can be taken higher via the live guest relocation capability of a clustered z/VM configuration, which enables you to move a running Linux image from one z/VM LPAR to another.
Back to dollar (or your local currency) savings: I haven't yet given you the whole picture with regard to the cost-efficiency advantages of Linux on System z. Those IFLs I mentioned are not only great performers, allowing you to do more Linux work with fewer engines -- they are also very attractively priced (and of course they have no impact on the licensing costs for z/OS software running on the same System z server). Want to get even more bang for your bucks? Check out the IBM System z Solution Edition for Enterprise Linux, an offering for existing mainframe systems that combines IFLs, memory, z/VM, and maintenance in a package that's a terrific deal.
Are you wondering who in your shop would administer Linux systems on a mainframe? That's easy: your current Linux system administrators would do the job just fine. During a Linux on System z proof of concept on which I worked a couple of years ago, I recall that a Linux pro in the client's IT department said something to this effect: "It's just Linux." Bingo -- and it's available in distributions from SUSE and Red Hat. What if your organization decides to bring in z/VM with Linux for System z (good move)? Who will take care of that OS, if it's new to your company? Answer: your z/OS systems programmers. First, there's a good chance that one or more of them have some VM experience (many mainframers do). Second, VM has been significantly simplified in recent years (for a "simple" install of z/VM, the instructions take up all of one page).
I'll close by reiterating the fact that Linux on System z is not some Johnny-come-lately solution. It was announced in December of 1999, and it's been regularly enhanced since then. Yes, it took a while for this System z configuration option to catch fire, but it is certainly hot now. If you have Linux systems that connect to DB2 for z/OS, running those Linux images on the same mainframe where the DB2 for z/OS data server runs can take the core of your IT infrastructure to new levels of efficiency, performance, scalability, security, and manageability. Get smart, and check it out.