Linux tends to be associated with x86 hardware in a business context, but some well-known companies are running it on mainframes.

"All of the large banks are using it [Linux on IBM System z], but don't want to talk about it," CA Technologies distinguished engineer Scott Fagen told iTWire.

Linux on System z has "huge advantages," he said.

Data warehouses and analytics systems typically run against systems of record that use IBM's DB2 database on System z: "the customers have spoken." Running Linux applications on the same mainframe rather than on smaller systems delivers performance improvements.

Organisations are tending to encrypt local networks to protect sensitive data flowing between systems, but that adds latency and slows the applications.

This encryption is not necessary if both systems are virtualised on the same hardware, and furthermore "you can't beat memory-to-memory speed," Mr Fagen observed.

He also sees the "repatriation" of systems to mainframes via Linux on System z. "Anything in Java just works," and IBM has been developing hardware to run Java applications very well, and CA Chorus provides "a tremendous improvement" in Java performance on new IBM hardware.

The big banks and insurance companies are "going after this pretty hard," he said, as it does not just reduce the cost of hardware and software, but also space, power and cooling requirements which are very important in some locations.

One mainframe can replace a large number of distributed systems, and the associated saving in network equipments "can be a real winner for a customer that understands what they are trying to get out of their system."

There is also a benefit when hardware upgrades are required, as IBM has a 'technology dividend' scheme that credits customers with a proportion of the cost of the capacity already owned. There is no equivalent in the distributed systems world, be said.

Disclosure: The writer attended CA World as the guest of the company.