Hi, in our organization we have exchange 2007 (2003 server): two backend (in cluster) and two frontend. On each frontend we have installed 4 GB ram and on each backend we have installed 6 GB ram. Searching on internet i found this information: " By default, Windows Server 2003 can address up to 4 GB of memory. The server doesn't actually need to have 4 GB of RAM installed though. Virtual memory allows Windows Server 2003 to address a full 4 GB, even if there is considerably less memory installed. Also by default, Windows splits the 4 GB of addressable memory right down the middle. It reserves 2 GB of memory space to the Windows operating system and 2 GB for user-mode processes (applications). The /3GB switch alters the balance of address space allocation. If the /3GB switch is applied, Windows will only allocate 1 GB of address space for the operating system, and leave a full 3 GB of address space for user-mode processes. Conventional wisdom has long stated that you should apply the /3GB switch to the BOOT.INI file for any server that has 1 GB or more of physical RAM. However, Exchange Server can be a demanding application, so the 1 GB rule may not always be what's best for Exchange Server. According to Microsoft, you should only use the /3GB switch on Exchange servers that are hosting mailboxes or public folders. If an Exchange server is simply acting as a front-end server, bridgehead server, or performing some other role that doesn't involve hosting mailboxes or public folders, it's best to allow the operating system access to the full 2 GB memory address space. (Microsoft did make the default 2 GB for a reason.) Some people at Microsoft have even suggested that the /3GB switch is best avoided unless Exchange Server is hosting more than 20 mailboxes. Microsoft also discourages the use of the /3GB switch if you are running Exchange Server on Windows 2003 Small Business Server, or if Exchange Server is running on a domain controller (running Exchange Server on a domain controller is not recommended). The primary reason for not using the /3GB switch in some situations is that the Windows operating system makes page table entries (PTEs) for allocating memory. Windows has a finite amount of space that it can use for PTEs, and using the /3GB switch significantly reduces the space available for them. If PTE space drops below a certain level, Windows has a tendency to become unstable. So it's often wise to provide the operating system with the full 2 GB of address space, unless Microsoft Exchange is the server's sole application and Exchange Server is hosting mailboxes and/or public folders. " In our case, how is the best practis to obtain the best configuration?? Best regards Massimo Valeri

Exchange 2007 must be installed on Windows Server 64 bit edition so, /3GB switch is NOT supported (in fact doesnt require since it can point up to 16TB in Windows 2003) in 64 bit edition. /PAE (Physical Address Extension) is also NOT supported in 64 bit edition. PAE is an Intel-provided memory address extension that enables support of up to 64 GB of physical memory for applications running on most 32-bit (IA-32) Intel Pentium Pro and later platforms only, not 64 bit. Reference: Comparison of 32-bit and 64-bit memory architecture for 64-bit editions of Windows XP and Windows Server 2003 Memory Support and Windows Operating Systems

Hi Massimo, I would like to explain that the FE/BE mode is no longer called in Exchange 2007 Server. It seems that you are using a mixed environment with coexistence of Exchange 2003 and Exchange 2007 Server. If possible, could you list more detailed information about your four Server systems version? For Exchange 2007, Microsoft recommend install it in x64 bit architecture Platform, I hope you have already installed it in the 64 bit platform. In this situation, you are not necessary to apply the 3GB switch in your Exchange 2007 Server. For your Exchange 2003 in 32bit server system, I highly suggest you read below KB articles carefully before applying /3GB and /userva Switches in your production server. Use of the /3GB switch in Exchange Server 2003 on a Windows Server 2003-based system http://support.microsoft.com/kb/823440/en-us How to use the /userva switch with the /3GB switch to tune the User-mode space to a value between 2 GB and 3 GB http://support.microsoft.com/kb/316739/en-us In my personal opinion, as higher memory requirement for store.exe in the BE Server, I suggest you give more memory on the User mode for Exchange backend Server, but we also need to consider the systems stable after reducing the system memory. Hence, Herein I would like to recommend you a Tool-Microsoft Exchange Best Practices Analyzer. After running this tool in each of your server, it will report a different results for advising. If the 3GB switch is not in the result, please take advise to apply it. If not in it, please do not apply it. For Exchange 2007, this tool has been taken in the toolbox of the Exchange management console, you do not need to re-download it. For Exchange 2003, please download the tool by click the below hyperlink: Microsoft Exchange Best Practices Analyzer v2.8 Download Link Thanks,

Thanks a lot and i'm sorry for my english.

Tanks a lot. I'm sorry for my english...and sorry for my uncorrect information. Our environment is only Exchange 2007 in x64 architecture Platform and iused the terms FE/BE for simplicity. I apologise for the error. Thank you very much, again. Massimo Valeri