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What are the pros and cons of running IIS as 32bit vs 64bit on a 64bit OS?

Asked 2009-02-03T16:24:25.663
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Possibly better suited for "Rack Overflow", but from a developer's point of view, what are the advantages and disadvantages of running IIS (serving both legacy classic ASP and .NET) as a 32bit process instead of a 64bit process on a 64bit windows host?

The main advantage of 32/64 (iis/server) over 32/32 seems to be the ability to go up to 4gb in memory per IIS process.

The advantages I expect of 32/64 over 64/64 appear to be that it's easier to access legacy 32-bit in-process DLLs (of which we still have one from a partner vendor we can't move away from immediately) and perhaps a smaller memory footprint for the same code given smaller memory pointers.

Are there any performance benefits of 64/64 over 32/64 or anything else that would warrant a full switch now? Have I made any false assumptions here?

asp.net iis 64-bit 32bit-64bit 32-bit
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I've had an experience where moving from a 32bit Windows 2003 Server to a 64bit Windows 2003 Server both running IIS 6 and the performance of the ASP.NET 3.5 website was unacceptable.

The 64bit server would run a clear 2 seconds behind the 32bit one consistently.

After switching IIS 6 to run as a 32bit worker process, the performance was equal and comparable once again.

I haven't verified it, but I think it might only apply to IIS6 win2k3, as testing I've done with IIS7 x64 (Vista) and a 64bit IIS worker process seems to perform just fine.

The process to swap to the 32bit process was quite simple. Here is the KB article with the supporting details: http://support.microsoft.com/kb/894435/en-us

ASP.NET 2.0, 32-bit version To run the 32-bit version of ASP.NET 2.0, follow these steps:

  1. Click Start, click Run, type cmd, and then click OK.
  2. Type the following command to enable the 32-bit mode: cscript %SYSTEMDRIVE%\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 1
  3. Type the following command to install the version of ASP.NET 2.0 (32-bit) and to install the script maps at the IIS root and under: %SYSTEMROOT%\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis.exe -i
  4. Make sure that the status of ASP.NET version 2.0.50727 (32-bit) is set to Allowed in the Web service extension list in Internet Information Services Manager.

See the KB article for setting back to 64-bit.

answered 2009-07-14T05:51:43.877

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