Exchange 12 and 64-bit

At the recent IT Forum conference in Barcelona, we started talking publicly about E12. It was great to talk with so many customers about the work we’re doing and get your feedback. One of the topics we discussed at the conference was the system requirements for which we are designing E12. I wanted to discuss one of these design points within this blog: requiring the 64-bit platform.


80% of the capital costs of an Exchange deployment are typically associated with storage. One of our primary E12 goals was to reduce these costs. Underlying today’s high cost is disk drive technology; specifically, that disk capacity is outpacing random IO performance significantly. According to Seagate, while disk capacity increased 15,000 times from 1987 to 2004, the random IO performance increased only 11 times during the same period. This presents a problem for any application that deals with large amounts of data; how to actually utilize this increased capacity while being constrained by such low IO rates. Customers either end up buying more storage capacity than they can effectively utilize (since the system is constrained by IOPS – IO per second), or buy faster, more expensive disks that match storage capacity with storage throughput.


In the E12 timeframe, 500 GB drives will be the norm and 1 TB drives will be available. E12 has been designed to leverage these large inexpensive drives, to lower your storage costs and enable you to provide larger mailbox quotas to end-users. Specifically, when comparing E2K3 to E12 on the same hardware, with the same user profile – but with a 64-bit OS vs. the 32-bit OS, our current tests show a >70% reduction in IOPS/user. In a future blog entry, we’ll discuss these improvements in detail.


In addition to these storage cost savings, there were 3 other benefits driving our focus on 64-bit:

  1. Scalability
    Exchange scalability is limited today by address space within the 32-bit Windows kernel. This fixed space has run out of elbow room, and gets tighter every day:
    • With the same # of users, an Exchange server today requires much more kernel space than a few years ago. On mailbox servers, connections per user have been growing over time: cached mode requires up to twice as many connections than online mode, mobile access keeps people connected more often, and folder sharing becomes more commonplace every day. Likewise, on the edge servers, spam can easily overwhelm an SMTP gateway with connections. For each and every one of these connections, precious kernel memory is reserved.
    • The OS itself continues to reserve more kernel memory for itself over time. With Windows 2003 SP1, with IPSec enabled and StorPort drivers being used, Exchange has 10% less space in the kernel to work with than it did with Windows 2003 RTM.

More great reading on these issues can be found within the kernel memory section of our Troubleshooting Exchange 2003 Performance white paper.

  1. Features
    Not having to worry about kernel memory starvation or IOPS exhaustion has freed us to deliver some great features. One of my favorite is aggregating individual Outlook-user safe lists out to the edge server, ensuring that any mail on an end-user safe list will get past server-side spam filters and make it to the user’s inbox. As you can imagine, even after all of the optimizations our engineers have dreamed up, this aggregation of all safe-lists in an organization can consume a large amount of memory – but we believe it is well worth it to make email becomes more reliable and secure.
  2. Co-existence with Outlook
    Outlook will co-exist great with E12 on the same server. This is because 32-bit Outlook runs in WOW. Many of you have been asking for this since the 2000 releases where this became unsupported.

Unfortunately, the optimizations we have made for the 64-bit platform cause the 32-bit platform to perform worse in many cases. Rather than fork the code base, and produce 2 different releases, one targeted to 32 and one targeted to 64, we thought it best to keep things simple and focus on one product. We will release a 32-bit version of E12 for feature evaluation, training, and demonstrations—but we are not planning to support this release in production.


Most servers shipping today are already x64-based, even entry level systems. You may have x64-based hardware in your environment already and not even know it. Because of the backwards compatibility of the x64 processors, 64-bit hardware can run 32-bit and 64-bit operating systems. If you are buying new systems today, to be ready for E12, look for systems with either of these 2 processors:

  1. the 64-bit Xeon processor or Pentiums with EM64T (NOT the Itanium or IA64). 
  2. any of the AMD64 processors (Opteron, Athlon and Turion). 

So how will migration work? The first thing to understand is that we are totally committed to full interop with E2K and E2K3 topologies. In fact, here at Microsoft we have 3000 people running on E12, with the remainder on E2K3 or even a few on E2K (for our sustained engineering team). The second thing which should make us all feel good is that all configuration data is mastered in AD – so we can introduce new servers into the topologies at any time, and the configuration data is always available to them. With that background, the migration process should be straightforward – introduce new mailbox servers running E12, and then “move mailbox” (which is now completely scriptable) the users across. The two places where things might get tricky are:

  1. 3rd party products. We are working closely with partners through our TAP program to ensure that they will be ready.
  2. Custom applications you have developed. The great news here is that all out-of-proc applications, e.g. those that use DAV, or those that use script interfaces, e.g. either WSH or ASP, will work unmodified. It is those applications which run in-proc to Exchange, that will need to be-recompiled 64-bit. Visual Studio 2005 provides great support for this re-compilation.

Lastly, we didn’t make this decision lightly. We understand that this will impact some of your planning- which is why we’re discussing it so early. We faced a trade-off of delivering an Exchange that tried to eke out a few $’s of savings on yesterday’s architecture, or a product truly optimized for today’s modern hardware that will deliver incredible cost savings to our customers.


Terry Myerson

Comments (33)
  1. Matt Drnovscek says:

    Speaking of Migration – any news if E12 will support any "rapid" migration methods? While moving mailboxes works its a slow & tedious process It took us longer than expected to move 16,000 users (about 4TB of storage) to new EX2K3 hardware. Any news of a supported forklift procedure? With today’s SAN technology it would be as easy as build a new server & migrate the disks to it instead of migrating one user at a time. This could cut down hardware refresh/migration time to mins, not weeks/months.

    Just wanted to add my 2 bits.

    Warmest regards,


  2. susan says:

    Who was the insane person who wants Outlook…a client app on a server? Mapi profiles can be used for SQL mail.

    I’m sorry but just because we admins are stupid enough to ask for something doesn’t mean you guys should do it.

    A server is a server and should not be running a client app that can introduce vulnerabilties.

  3. Rick says:

    Re: 3rd Parties. Even though RIM and MS are competitors, I hope you are going to ensure that E12 works nicely with BES. Our org cannot live without it.

    Outlook on a server? I would fire someone for doing such a dumb thing.

  4. aaron says:

    Regarding Outlook on a server… on a limited basis for testing or a specific purpose, I don’t really see an issue. On a critical production server, I admit it is a bad idea.

  5. Regardind Outlook on a server: It’s not always the "stupid" admins… It’s also 3rd Parties requiring Outlook to be installed on the exchange server… For example Backup Agents for Brick Level Backups…

  6. Yuhong Bao says:

    What about running Exchange Server 2003 on Windows Server 2003 x64 inside WOW64? The /LARGEADDRESSAWARE applicatons, including Exchange Server 2003, will get a full 4 GB of virtual address space, and all applications will still get the benifits of the larger 64-bit kernel address space.

  7. Uli Zug says:

    You suggest to buy Intel EM64T and AMD64 processors and not Itanium to be E12-proof.

    What is the reason for this recommedation ?

  8. Tony Redmond says:

    Re IA64, HP believes that Microsoft has no plans to produce a version of Exchange 12 that runs on Itanium. This makes sense because relatively few people use Itanium to run Windows… I think that the real issue is to make sure that Exchange runs well on the Intel and AMD x64 mainstream processors before seeking to conquer the entire 64- bit world.

    – Tony

  9. Dan Sheehan says:

    It just affirms that this is one of the best sources of information for Exchange on the web.

    Thanks to all for all the great content.

  10. Sandeep Naidu says:

    Does the MAPI subsystem of Exchange12 support Unicode services as Outlook 2003’s does?

    I guess the move for providing the ability to run Outlook on Exchange12 has got more than a testing perspective as Mr.Christian Schindler said.

  11. Sandeep Naidu says:

    Does the MAPI subsystem of Exchange12 support Unicode services as Outlook 2003’s does?

    I guess the move for providing the ability to run Outlook on Exchange12 has got more than a testing perspective as Mr.Christian Schindler said.

  12. scoturner says:

    Although I haven’t seen it mentioned, is there any chance that E12 will support clustering of Exchange *data* and/or replication of mailboxes to multiple servers to provide redundancy and failover? Thanks.

  13. Scott: yes, E12 includes some new redundancy features. MS hasn’t talked much about the details, but the feature you’re interested in is the continuous protection feature– look for more details here in the future, as I’m sure it’s something they’re eager to talk about.

  14. Ruwan says:

    Pls tell us how the 3rd world country can afford and use E12 ?

  15. greygoose says:

    Will Exchange 12 support migration from 5.5?

  16. Marcus Souto Jentzsch says:

    I´m starting to plan a new Exchange Server Deployement in my company and I wanted do purchase new hardware to install Exchange Server 2003 and later have the ability to upgrade to this new E12 version on the same hardware. It seems that this is not possible due to the fact that E2k3 runs exclusively on 32 bits procesor and E12 will run exclusively on 64 bits processor. This doesn´t make sense to me. Is there a solution to this problem?

  17. Exchange says:


    Yes, you should buy 64 bit hardware. Note though that the x64 is the way to go as far as Exchange is concerned, as Exchange 12 will not run on I64. x64 can run 32 bit Windows and Exchange 2003 until you are ready to move to 64 bit Windows with Exchange 12. Please see the following for more information:

  18. Craig says:

    Existing (In use) X64 compatible hardware is a bit of a waste of time isnt it, when the only way to migrate is to "move mailboxes" to a new Windows/Exchange12 64bit server !

    I understand the concept if an in place upgrade were available. And I understand the reasons why you couldn’t (That is unless there is a new approach to upgrading). Ex2000/2003 has kernel drivers, thus needs a 32bit kernel and obviously 64bit Ex wouldn’t work under a 32bit OS. And so on

    I know, use a swing server…..

    Just thought I’d comment…

  19. Craig says:

    Hey will there be a way to Disaster Recovery to a 64bit/Ex12 version ?

    And at the same time have E12 compatible with Exchange2003 databases, or upgrade them when detected ?

    I think you get what I mean right ?

  20. Exchange says:


    If you mean if "In case that E2003 server goes down if you will be able to bring up an E12 server in it’s place by running a /disasterrecovery setup from E12" the answer would be nope – this is not a tested scenario or something E12 is designed to do.

    At this time I do not know what would happen if you restored an E2003 database to an E12 server and tried to start it up.

  21. Anonymous says:

    A frequent topic of discussion with customers is the future of Public Folders, thus I think it would…

  22. emsquared says:

    Is there any more information you can share regarding the following snip from this entry?  

    "with a 64-bit OS vs. the 32-bit OS, our current tests show a >70% reduction in IOPS/user."

    For those of us in a storage platform upgrade/purchase cycle this info will durastically impact spindle type purchased.  Considering magnitude of this investment any info you can provide now regarding IOPS reduction greatly appreciated.

  23. JFN says:

    First) The IT folks who are wondering why Microsoft made it possible for Outlook to be installed on the same system have obviously not worked as an Exchange admin for long or they would understand that some programs require this program. It’s not so you can read your email. "duh"

    Second) The one thing that wasn’t mentioned here is the ability to fail over an exchange server in a none clustered environment without effecting your users. For that alone it is worth purchasing. We will be implementing this solution when E12 is released.

  24. Anonymous says:

    Kokią kompiuterių įrangą turėčiau įsigyti, jeigu jau dabar noriu naudoti Exchange Server 2003, bet tikiuosi iškart migruoti į Exchange 12 vos tik jam pasirodžius? Ar draugaus naujasis Exchange 12 su Public Folders technologija?

  25. Anonymous says:

    Following the December blog entry on Exchange 12 and 64 bit, Harold Wong asked me to record a podcast…

  26. Anonymous says:

    The team over on the Exchange Blog (You Had Me at EHLO…) have just posted a podcast interview of Terry…

  27. Anonymous says:

    Just leaving the office this evening and I got a great question from one of our execs to round out the…

  28. Anonymous says:

    След една от презенатациите, които изнесохме в Университета за Национално и Световно Стопанство (част…

  29. Anonymous says:

    I wanted to give you an intial heads up as to what to expect in E12 this post is just a very high level…

  30. Anonymous says:

    I promised to give links to everything I talked about at this mornings TechNet event on Exchange 2007

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