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I am getting a Windows server with the option for Windows Server 2008 32-bit and Windows Server 2008 64-bit. I will only be running IIS7 and SQL Server 2008 Express. Which should I use and what are the indications?

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bear in mind there is Server 2008 SP2, which is 32 and 64 bit, and Server 2008 R2 SP1 which is 64-bit only. –  tombull89 Jun 9 '11 at 10:32
As Tombull says R2 is 64bit only - and is the most current version of the OS. I would go with the most current if I were you. –  Chadddada Jun 9 '11 at 13:24
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2 Answers 2

up vote 2 down vote accepted

If you need to run 64-bit applications such as Exchange Server, you need 64-bit.

If you have more than 4 GB of memory, or plan to have them in the future, you need 64 bit.

Also, keep in mind that the next Windows releases will only be 64-bit (Windows Server 2008 R2 already is), as well as all Microsoft server products; so it's best to move forward as soon as possible.

Generally speaking, there is no reason to stick to a 32-bit server O.S., unless you need to run applications (or to load drivers) that don't work on a 64-bit one. IIS on 64-bit systems is also able to work in 32-bit compatibility mode, if you have this need.

BTW, why are you getting Windows Server 2008, instead of the more current Windows Server 2008 R2?

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I'd add that 32-bit versions are more memory- and storage-efficient due to less overhead, so if you do not need the 64-bit features of a larger address space and are short with RAM and HDD space (as for example would mostly be the case with VMs), you should stick with 32-bit versions. –  the-wabbit Jun 9 '11 at 10:26
In my experience the extra RAM footprint of a 64-bit OS and 64-bit apps is relatively small, so if you are working with machines or VMs with 1Gb RAM or more you are better off using the 64-bit variant flexibility now or later. The disk space footprint for Windows seems much more significant between 64 and 32 bit variants though, mainly due to always having both versions of many libraries stored in case needed, so this is a more compelling reason to recommend 32-bit variants in VMs. –  David Spillett Jun 9 '11 at 12:01
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As I understand it, Windows Server 2008 R2 and onwards will be 64bit only. It's the way of the future because most processors out there are now 64 bit.

You can still run 32-bit applications under 64bit windows although device drivers must be 64bit. I've run into some occasional issues with 32 bit applications. However, I've usually managed to get them to go though either will a little tinkering of the system and/or finding the missing 32-bit libraries they need.

So, clearly the shift is away from 32 bit applications. Go with 64-bit where possible.

I would only use 32bit Windows Server if it can't run on the hardware that you have. But then if your hardware is that old I think you should consider upgrading that.

Some 64bit processors are missing the virtualization extensions. Although they can run 64bit windows natively, they can't load it virtualized on the same hardware. In that case, we had to run Server 2008 R1 32bit. This problem was found with some now obsolete IBM HS20 Blade servers so watch out for that.

EDIT: I should add that all major virtualization platforms these days utilize the processor virtualization extensions (for Intel that's VTx). These are required to load 64bit OS's onto them. You also need a native 64bit host OS unless you're using something like ESXi. i.e. if you loaded Linux 32bit and installed VMWare Server you won't be able to run a 64bit windows virtual machine on that. But if you have 64bit linux host you can run 32bit or 64bit windows virtual machines on it.

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64-bit processors for INTEL have been around since 2006. Basically they have VMM extensions if they are core processors...regular old XEON processors do not, but can run x64 natively. –  KCotreau Jun 9 '11 at 13:05
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