Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

Weird question: In the office whe are discussing if whe have a machine that is 64bit infrastructure (hardware) with a 32bit OS (Server 2008 std) and 8 gigs of ram.

The OS detects the full 8 gigs of ram, BUT, being a 32 bit OS, will the OS use the full 8 gigs of ram?

How can we prove how much ram is really being used, or Windows Server is fooling everybody?

more: whe need some tests done, is there any benchmatking software out there for this purpose?

share|improve this question
3  
Why the downvotes? –  Axel Gneiting Mar 23 '11 at 23:39
1  
^^ This. This is quite an interesting question with some useful stuff coming out of it. –  Linker3000 Mar 23 '11 at 23:46
add comment

3 Answers

SQL Server definitely uses it with AWE enabled so there's your not-just-theoretical proof. Even without AWE, any one process could only access 2 GB but if you have multiple such processes you can use it all.

share|improve this answer
add comment

You could try to verify it by disabling swap space and creating some 2g consuming processes. Consuming as in random data (to prevent Copy-On-Write and lazy access to unused pages).

share|improve this answer
add comment

A 32-bit OS using PAE can access up to 64GB of physical memory, but a process running on it will still be restricted to 4GB unless it uses a hack such as AWE.

share|improve this answer
    
Even with PAE, the 32-bit kernel has hard-coded memory limits for a few purposes. So you may have unused memory and still be memory starved. –  Zoredache Mar 23 '11 at 23:32
    
plus using PAE is usually slightly slower –  mbx Mar 23 '11 at 23:33
4  
This is not entirely correct. One process can only use 2 GiB of virtual address space when running on 32 bit Windows, because the rest is used by the kernel (3 GiB if the /3G kernel parameter is used and the executable has the "large address aware" flag set). –  Axel Gneiting Mar 23 '11 at 23:36
    
@mbx: Context switches are certainly more costly, but is this really measurable? –  Axel Gneiting Mar 23 '11 at 23:38
    
@Axel: Sure, but it can still access 4GB, even if it can't write to all of it. –  Ignacio Vazquez-Abrams Mar 23 '11 at 23:56
show 4 more comments

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.