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What makes a migration from Unix to Linux attractive?

Learn about Linux's attractive qualities such as platform flexibilty, quick deployment of patches, and better compatibility and cost structures. Calculating the return on investment (ROI) of migrating from Unix to Linux is also presented.

Editor's note: This is the second part in a series of articles on Unix-to-Linux migrations on

Now that you understand what the challenges are that Unix faces, what is it about Linux that makes it so desirable?

  • Platform flexibility: Linux can run on anything, from commodity-based x86 servers to Unix vendors' hardware, such as IBM Power Systems, HP Itanium, x64 AMD Opteron-based systems and Sun Ultra Sparc and even IBM mainframes. No other OS can match the flexibility of platforms that Linux offers, which means that your business has the flexibility to change platforms as it requires.
  • Deployment of patches: Traditional development cycles can be endless with commercial vendors. Coming from the open source world, Linux is built to be modular. The software is accessible so you can fix it yourself, or community developers can come up with a patch quickly. With Unix, you're usually locked into your vendor's hardware and that leaves you with fewer options to save money. No other OS can match the flexibility that Linux offers. And flexibility can translate into cost savings.
  • Compatibility and cost: Ever try to price out an application on Linux and then the same application on Unix? Invariably the Linux license comes out cheaper. And although it's possible to run open source applications on Unix, open source and Linux go hand in hand like peanut butter and jelly. If availability is important, you cannot go wrong with Linux.

You only need to look at HP's decision several years ago to stop support for its Tru64 version of Unix. People are still angry about that today because Tru64 support for new technologies are no longer available. With Linux, you don't have to worry about being caught up in a vendor's decision or restructuring. Even if one of your Linux vendors goes south, the kernel itself is maintained by Linux.

Evaluating the ROI of Migration
Migrating from any system to any other system will cost money, no question about it. What makes a migration project worth performing is its return on investment (ROI). The ROI is calculated with this metric:

ROI = Cost savings * 100 / investment (or TCO).

With Linux, make sure you measure the costs of the acquiring the hardware as well as the costs of software, migration, training, maintenance and day-to-day operation. Also remember that certain costs are one-time only. Staying with your current systems may include upgrades to hardware and software. So when considering a migration, compare it not only to what your costs are today but also to what it will take to get up to speed for a modern Linux deployment.

To calculate the ROI, determine the initial cost of the project, which should include the cost of development, hardware, migration, maintenance and support. This includes human capital. At the end of the day, you'll try to project the annual savings that the company will have when you are ready to go into production. Usually you'll want to do this over a three-year period.

You can choose from several methods to calculate long-term cost. The one I like to use is Net Present Value (NPV), which is the present value minus the initial cash outlay. Most finance professionals use this method. There are a lot of numbers to crunch in the NPV method, but you must do this to show your business that it really makes financial sense to migrate from Unix to Linux.

When quantifying the TCO, break it down into one-time costs and ongoing costs. One-time costs include software licenses, hardware, consulting costs and training. Ongoing costs include hardware maintenance, software maintenance, license maintenance fees, software upgrades and ongoing training.

One of the most compelling reasons to migrate is the annual savings on database licenses alone. Usually when you migrate, you also consolidate. That enables you to run with fewer CPU cores, which can dramatically increase cost savings.

The next part in the series shows you how to port applications from Unix to Linux.

ABOUT THE AUTHOR: Ken Milberg is the President and Managing consultant of PowerTCO (formerly known as Unix-Linux Solutions), a NY-based IBM Business Partner. He is a technology writer and site expert for and provides Linux technical information and support at

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