There has been alot of discussion on using Windows Server 2003 64-bit edition for an Active Directory Domain Controller (DC) lately.

Brian Puhl posts some insightful information on his blog, which offers details on Microsoft’s internal 64bit environment.

Joe is seeking some results from the field on those who are paving the 64-bit DC way.

Of course, I would start with the Microsoft whitepaper: Active Directory Performance for 64-bit Versions of Windows Server 2003.

Anyway, in discussion today about AD planning today,  we were talking about the move to 64-bit to DCs, and I had wonder what effect this will have on the limit of 300mb aggregate limit for Event Logs on domain controllers.  Will going to 64-bit, allow more memory space for services.exe to increase the log sizing in remote DCs?

Despite what seems to be a way to set the log size to 4gb, Microsoft recommends (KB 183097 references 32bit only) the 300mb limit, which I am going to assume is on the 32-bit OS.

“The Event Log service uses memory-mapped files, and it runs as one of the services under the Services.exe process as Eventlog.dll. When files are loaded in this way, the entire file is loaded into the computer’s memory. All of the current versions of Microsoft Windows® have an architectural limitation with regard to memory-mapped files: no process can have more than one GB of memory-mapped files in total. This limitation means that all of the services that run under the Services.exe process must share the one GB pool. The memory is assigned in contiguous 64 KB portions, and if the computer cannot assign additional memory to expand memory-mapped files, problems will occur.”

So it does say all current versions, with this article being written in December of 2005, (another here from 2003), I am not sure if this applies to the 64-bit versions.

If you know if the 1gb per process limit exists in the 64-bit version, please let me know.   The 64-bit hardware is being racked in the lab this week, so hopefully I will know.