Iphone

Recently ran across this exchange in a forum - My question is whether there is actually a chance of degrading the performance if the page file size is set too large? --

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"Having recently increased my RAM from 512MB to 2.5GB, I would like your suggestion on what values to set the page file for the min and max sizes."

Ray, how large a pagefile to use depends on how many applications you need to have open at any one time. It also depends on how much RAM those applications need to operate efficiently. Figuring that out can sometimes be difficult, especially when your application usage habits change.

It's usually best to let Windows decide how it should manage the pagefile size. To do that, follow these steps for Windows 2000 and XP systems:

Step 1. Right-click on My Computer and select Properties.
Step 2. Select the Advanced tab.
Step 3. Click the Settings button in the Performance section.
Step 4. Select the Advanced tab.
Step 5. Select the Change button in the Virtual memory section.
Step 6. Select the drive that contains your pagefile.
Step 7. Select "System managed size."
Step 8. Click OK to close each of the open dialog windows.
Step 9. Reboot your computer.

If you feel that you must control the pagefile size yourself, then with 2.5GB of RAM in your system, consider using a pagefile of the same size. If that turns out to not be enough for your needs, consider increasing the ratio to 1.5 times the amount of physical RAM.

Iphone

Generally 1.5x is a good guideline for normal servers And 4095MB is the max you can set in 32 bit os unless you hack the registry and separate pagefile in directories.
See this:
Pagefile Optimization

With 64 bit OS you can go well above the 4095MB limit, I'm not sure but we have a 16GB server with a 1.5x pagefile on 64 bit OS.

One theory is you can have too much pagefile. Some applications will use whatever memory it can grab. This includes the page file. You can imagine swapping in/out of memory to disk is slow. If you have a large pagefile, the app will end up using virtual memory on the disk. Thus if you have a server with 16GB of RAM and a 24GB pagefile, it might actually run slower than if you had 16GB of memory and only an 8GB pagefile because with the smaller pagefile, it will be forced to use more real memory than virtual memory.
However, I've never seen this personally. SQL is about the only app I know that uses memory is vast quantities like this and SQL is smart enought to handle this.