Ask The Perf Guy: Sizing Guidance Updates For Exchange 2013 SP1

With the release of Exchange 2013 SP1, it’s time to revise our sizing guidance given feedback from customers, observations from our own large-scale deployments, and requirements associated with new and changed components in SP1. In addition to this brief article, I’ve also updated the original blog post with updated formulas and tables to reflect the changes described here.

There are two specific changes that need to be highlighted:

CAS Processor Sizing

With the introduction of the MAPI/HTTP protocol, our existing sizing guidance for CAS processor utilization needs to be changed. Usage of MAPI/HTTP has a fairly dramatic increase in rate of requests handled by the CAS role, when compared to requests generated by clients using RPC/HTTP. As each connection has a measurable amount of processing overhead, this results in an overall increase to our CPU requirements on CAS, moving from a 1:4 ratio of CAS to Mailbox processor cores, to a 3:8 ratio (a 50% increase). It’s important to call out that MAPI/HTTP is disabled by default, as we expect that customers will want to carefully evaluate the deployment requirements and impact of MAPI/HTTP before enabling it. Because it is disabled by default, existing Exchange 2013 deployments do not need to immediately add more CPU resources at the CAS layer. Instead, we expect that additional capacity will be considered as part of the evaluation and deployment process for MAPI/HTTP. We do anticipate that over time it will become the standard method of connectivity for Outlook clients so it’s important to include these requirements in our sizing guidance as early as possible.

It’s also critical to deploy .NET Framework 4.5.1 if you intend to use MAPI/HTTP, as it contains an important fix that impacts the performance and scalability of MAPI/HTTP at the CAS layer.

Ross has updated the Exchange Server 2013 Server Role Requirements Calculator to take into account this guidance change in version 6.3.

Pagefile Sizing

As memory requirements have increased for Exchange, our historical guidance for sizing the pagefile has become more and more challenging from a deployment perspective. Previously, our guidance was to set a fixed pagefile size equal to the size of RAM + 10MB. On servers that are commonly deployed with 128GB of RAM or more, requiring a pagefile sized to RAM+10MB results in a large amount of space consumed (typically on the system drive) with questionable benefit. In our large-scale internal deployments, we have been running with a cap on pagefile size for quite some time, and as a result we are comfortable recommending that all of our on-premises customers follow that same guidance. Moving forward with Exchange 2013, we recommend a fixed pagefile of the smaller of RAM size + 10MB or 32,778 MB (which is 32GB + 10MB). Hopefully this will free up some needed space on your servers.

As we continue to learn more from customer feedback and monitoring of our own deployments, we will keep updating this guidance via posts to the blog.

Jeff Mealiffe
Principal Program Manager Lead
Exchange Customer Experience

Comments (20)
  1. Petri X says:

    Is there any good explanation for the question: Exchange 2013 with 96 GB RAM, where do we need pagefile?

  2. @Max – No. The guidance changes that Jeff discussed in the above article are baked into the calculator in v6.3 and later. that way it doesn’t matter. All future environments will be sized with MAPI/HTTP load being considered and if you want to validate whether you have the headroom to enable MAPI/HTTP for existing designs, then you can re-run your numbers in the new calculator and compare with what you are seeing in production.


  3. Milind Naphade says:

    Jeff, does the guidance for pagefile sizing mean that 32 GB + 10 MB is sufficient for any memory size on a server? In case there are third party products installed on an exchange server perform excessive operations in memory wont that hit the overall performance of the server?

  4. Anonymous says:

    Looks like the Exchange 2013 Server Role Requirements Calculator has been updated already.

    Good news on the page file size!

  5. Jeff, I mean the fixed page file size RAM size + 10MB or 32,778 MB (which is 32GB + 10MB).

  6. I mean network traffic bandwidth sizing for MAPI/HTTP traffic

  7. Exchange service pack 1 information. thank for your article.

  8. Anonymous says:

    @Exchange Queries – Not sure exactly what you are asking with the 32GB question. Is this related to the pagefile guidance, or other memory guidance? Regarding MAPI/HTTP network bandwidth consumption, I know there is some ongoing work to provide details on the impact of the new transport protocol. It’s not ready quite yet, but when it is, you’ll see it on the blog. We do expect an increase in bandwidth consumption, and it should be related to the authentication protocol being used (as auth headers can vary dramatically in size across the different auth protocols).

  9. Recep YUKSEL says:

    Thank you This Team.

  10. Hi Jeff will Ross add the MAPI/HTTP yes/no setting to the “Exchange Environment Configuration” of the fabulous Echange Server Role Requirements Calculator? In version 6.3 I was not able to find this setting. Regards Max

  11. Nice Article Jeff, How about the MAPI/HTTP traffic and also is there any specific calculation to pick 32 GB for memory either not 24 or 48 GB

  12. Bram says:

    To summarize: for every 2013 SP1 deployment a 32GB + 10MB pagefile is sufficient?

  13. will says:

    Looks like Outlook 2013 SP1 is the only client that can use this – for now.

  14. Jeremy Wood says:

    Would this page file limitation apply to Exchange 2010 as well?

  15. Chase says:

    How many times do I need to resize an environment? RTM came out months before any sizing guidelines and now we are in April, over a year after the release, and we have new requirements. Do we find this acceptable in an Enterprise environment? My 2010 sizing’s lasted me 5 years, my 2013’s lasted me 6 months.

  16. Jeremy Wood says:

    Is this page file guidance a good rule to use with Exchange 2010 as well?

  17. Satguru Sharma says:

    PageFile Sizing – does the guidance mean that for any server with more than 32GB of physical memory, we need to keep the pagefile size to 32778MB or is there a ratio to keep based on the amount of physical memory. What does “Smaller of RAM size” mean?

  18. Erick says:

    I am also confused with the statement that says “smaller of RAM size”, do you mean smaller physical DIMM installed?, if I used only 16Gb on my MBX inside a virtualized env, where the hosts uses DIMMs of 8GB (and memory is dedicated to this particular VM), how do I define that calculation?

  19. Jeremy Wood says:

    Can the same be said for Exchange 2010 or are we stuck with using too much drive space for a pagefile that won’t be used that much?

  20. Jeff A. says:

    Could you please change the 2013 System Requirements page to reflect the new pagefile guidance?
    This here, under hardware –

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