It's a great server OS, sure, but lets look at this realistically:
- the Windows / .NET trading system was based on Windows 2003 and SQL 2000, and was deployed in 2005.
- the Linux-based system is under development now, to be deployed next year.
- the Windows / .NET trading hardware has been upgraded continuously because it was unable to cope with the load.
Just based on that, you'd expect substantial performance differences from just using newer hardware.
Sure, except for the part that the both are running on new hardware.
Chances are that the original kit was certified as a part of the solution, and hasn't been replaced since.
"Chances are" - except that is 100% wrong. They had problems since day 1, which were blamed on the hardware, so they've been constantly upgrading it trying to fix the problem.
Even ignoring the hardware and the OS, one would expect 90% of the performance to be determined by the application, not the OS. Decisions like writing the software in .NET versus C or Java, or using a special-purpose Java runtime would make a huge difference, irrespective of the OS.
The old system was written with the help of MS. They were the ones that said that .NET was the best way to implement it, and they even touted this in their press releases.
On top of this, the software stack is completely different, and developed by a different team. Just about every design decision, small and large, will be different.
Of course it's completely different - that's the entire fscking point.