A series of posts by Microsoft’s Enterprise Platforms Windows Server Performance Team outlines exactly what it will take to
move your existing servers to WS2008. For the most part, if you are running Windows Server 2003 (R2, SP1 or SP2), you will be guided to upgrade to the same-named edition of WS2008. That is, the standard edition of 2003 should support a full installation of the standard edition of 2008; the same is true for Enterprise Edition and Datacenter Edition. You cannot, however, upgrade from an x86 version to an x64 version. The team also notes that the WS2008 for Itanium is an exception (although they do not specify what would be required to install it).
Other issues regarding resource requirements are also spelled out in the post. Here’s an excerpt.
With respect to resource limits, there are also some changes to be aware of. Many values that are dynamically configured for 32-bit versions of Windows Server 2008 are set to their maximum values in 64-bit versions since the virtual address range is much larger. The notable exception to this rule is the NonPaged pool which is dependent on the amount of physical RAM installed. The table below outlines the resource limits:
| Memory Type | 32-bit Windows | 64-bit Windows |
| User mode virtual address space for 32-bit processes | 2 GB (up to 3 GB with 4GT RAM tuning) | 2 GB (4 GB with IMAGE_FILE_LARGE_ADDRESS_AWARE) |
| User mode virtual address space for 64-bit processes | N/A | 8 TB on x64, 7 TB on IA-64 (2 GB without IMAGE_FILE_LARGE_ADDRESS_AWARE) |
| Kernel mode virtual address space | 2 GB (1 GB to 2 GB with 4GT RAM tuning) | 8 TB |
| Paged Pool | Dynamic – limited by kernel mode virtual address space and physical memory | 128 GB |
| NonPaged pool | Dynamic – limited by kernel mode virtual address space and physical memory | 75% of RAM up to a maximum of 128GB |
| System cache virtual address space | Dynamic – limited by kernel mode virtual address space and physical memory | 1 TB |
| Desktop Heap | 3 MB for interactive desktop by default, however this is a tunable value | 20 MB for interactive desktop by default, again this value is tunable |
| System Page Table Entries | Dynamic – limited by kernel mode virtual address space and physical memory | Dynamic – limited by kernel mode virtual address space and physical memory |
| Maximum registry hive size | 2 GB* | 2 GB* |
* – the maximum registry hive size excludes the System hive. The System hive size is determined as follows:
- x86: 400 MB or 50% of physical memory, whichever is smaller
- x64: 1.5 GB or 50% of physical memory, whichever is smaller
- IA-64: 32 MB
Few enterprises will be in a hurry to conduct immediate upgrades on existing hardware, research indicates. Most will likely upgrade when the server requires a hardware refresh.
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Like this? More posts on WS2008 from Microsoft Subnet
A step by step on how to add a role to Server Core
How to get started with Server Core in WS2008
Let’s Get Reacquainted & How to Optimize Windows Server 2008 for Branch Office Communications (Four Part Series)
Windows Server 2008 Management and Maintenance tips
Fabulous giveaways from Microsoft Subnet and Cisco SubnetAll Micronet blog posts
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