Performance impact of Win32 + PAE on a JVM

Hi,

one of my clients insists on installing a Windows 2003 Entreprise OS on a 32 GB RAM server. My application is a java web application (servlet) mostly reading a datawarehouse. This DWH will be running on Oracle 10g.

What will be the impact of this OS choice ?

It seem from my tests that I cannot assign a heap space bigger than 1.5GB (Xmx) to my JVM. Also, I don't know what the impact on Oracle will be.

What are the pros and cons of this OS choice ? (license cost maybe ?)

Thanks

PS: our primary advice was Debian (64bits) / Postgresql, but, you know, customer is always right :-)

From serverfault alci

• "PAE does not change the size of the virtual address space, which remains at 4 GB. It changes only the actual RAM that can be addressed by the processor." (http://support.microsoft.com/kb/2267427/en-us) The way Windows arranges memory further restricts the practical maximum heap size to about 1.5GB because shared libraries are loaded at the 2GB limit and the /3GB switch, even if available, does not help much. With the /3GB switch max heap size is 1.7 - 1.8 GB: http://www.ibm.com/developerworks/java/library/j-nativememory-linux/.

  Chris S : Also keep in mind that PAE works by changing the 4GB that the processor can address at any given time. There's a penalty to switching too, so if you're using more than about 8 or 12 you really start to notice the switching lag and memory access gets slower with the constant flipping.
  From alip

• I am a bit rusty on this (8i and 9i was my forte), but on Oracle, you used to be able to use the extra memory that was available via PAE. It was not available to the Oracle process space (per the normal 32 bit limitation), but it could be used for the Buffer cache.

  From Brice