How Hard is it to Manage Different Unices?

vrmlguy asks: "Where I work has several Unix-based servers, all running the same vendor's OS. We are getting ready to buy another big server, and management wants to get bids from other vendors. However, our staff is only familar with our current vendor's OS. Yes, I know that any two flavors of Unix are more alike than not, and yes, I know about the Rosetta Stone for Unix that makes it easy to transfer skills. I want to know about the down-side: What's the difference in the cost of operations between a mono-culture and a shop running two or more vendors' OSs?"

Comments

Software costs

[Krieger]

Are what's going to kill you. Having to support software and software interoperability between different platforms can be a serious pain. A mono-culture is easier when dealing with software. However if you are presented with a significant enough savings from another platform, consider it.

Your admins, if they're any good, should be able to adapt to a different UNIX easily. Yes there are differences, but not ones that should trouble an experienced admin any longer then it takes him to read a couple man pages.

Complexity is the answer

[.@.]

The reason homogenous environments are easier to manage than heterogenous environments is due to complexity.

Simply put, if every server and workstation is identical, interoperability is not an issue, and the work associated with tracking, testing, and applying changes to that one, homogenous OS image is minimal.

The moment you branch out into different configuations of the same OS version, different OS versions, or different OS platforms, you've increased the complexity of the system, and thus increased your workload. Suddenly, interoperability is a factor in every decision, and issues with multiple versions and/or vendors must be tracked.

I've been meaning to write a short paper on this for some time, and attempt to relate it to Christopher Langton's Lamba parameter for the measurement of complexity (in the 3rd Annual Proceedings of the Artificial Life Conference). I've studied the identification of single points of failure for some time, as well as the question of "how many sysadmins do I need?". Both answers are directly related to the complexity of the system being managed (here, defining "system" as the collection of applications, OSes, hardware, and networks that comprise the scope of a sysadmin's responsibility). There are indeed identifiable factors that define the heterogeneity of an environment, and the ways in which these dimensions impact such things as the number of SA's required to manage them can be defined.

UNIX geeks perspective

[jregel]

I've no idea about the cost issue, but as a UNIX geek, the more versions of UNIX the better. I like the subtle differences and would hate it if there were only a single version.

Knowing that (as an example) AIX has a pretty self tuning kernel, that Solaris has a modular kernel, and that UnixWare needs a recompile (relink) for any minor changes forces the admin to think about the operating system instead of just drooling on the keyboard.

The biggest differences are still SysV vs BSD. Understanding those is vital in a mixed OS environment. Beyond that, there are usually differences in disk layout (and filesystems), but they just add to the rich diversity that is my favourite OS.

At my work, we are big users of Solaris, but because we develop software for multiple platforms, I've also had exposure to AIX, UnixWare, Sequent Dynix/PTS, HP-UX and DRS/NX. These days we've dropped Dynix/PTS (EOL anyway I think), HP-UX (too expensive for our customers), and DRS/NX (dead?) but we're looking to port to OpenUnix 8 and Red Hat Linux, so things are still pretty mixed. I just think it's a shame that I don't get to work with HP-UX and that Unixware is dying (yes - I like it!).

We also port to NT/2000, which is good to compare - it's a nightmare to work with when used to UNIX.

Re:I see it like this...

[Zeinfeld]

My experience is that in the 1990s when we ran an all DEC shop we got our DEC prices on hardware down by 10% when we bought a sun box. At another institute we saw a similar effect with SGI.

The price advantage you see is likely to depend very much on the type of computing you do and the volume. If you only buy 5 machines a year I doubt that the price break you get by going to a multivendor environment is going to be worth loosing binary compatibility for, let alone the admin hassle. If on the other hand you buy 100 machines a year you should definitely get a second vendor in place.

The other issue is that the price gap from Sun to Intel is huge. Comparing machines of like performance Intel boxes can be up to a third of the cost. Unless you have a real definite need for the features of a non-Intel platform (and I can't think of many offhand) the cost saving of Linux or BSD can be great.

I can't think offhand of any reason to have six vareties of Linux arround unless you are a masochist of some sort.