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smp_86112's avatar
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Dec 07, 2011

LTM Sizing for Exchange 2010

I am being asked to provide load-balancing in support of an Exchange 2010 implementation. I was wondering if there are any published guidelines on how to decide which hardware platform to use? Is there some sort of algorithm that converts Exchange statistics into LTM statistics?



We are looking at one site with 4500 users, and another with 10000 users - the sites will be using separate LTM pairs. I would be interested in hearing what hardware platform other people are using with a similarly-sized Exchange 2010 environments.





6 Replies

  • We run around 30,000 Exchange 2003 mailboxes on a old LTM 3400. I imagine a 1600 would probably probably be able to handle the load just fine. Don't be sold on the SSL TPS for just Exchange use. I also host 130,000 Exchange 2007 mailboxes on a pair of 6900s. Our sustained SSL TPS hovers around 4-500, bursting to around 2-3,000 if we perform a failover.
  • Helen_Johnson_1's avatar
    Historic F5 Account
    Hi smp,



    While Casey has some valid advice, it would be prudent to engage your local F5 account team, if nothing else to do some whiteboarding on what your deployment will look like. Exchange 2010 has some very different architectural requirements from Exchange 2003, which will put more demand on the services that a BIG-IP provides. If you need assistance on finding out who your local team is, please let me know, and I can find that out for you.





  • Casey,



    What is the primary access method for your Exchange environments(OWA, ActiveSync, RPC, RPCoverHTTP, etc.), and what is the concurrency of the connections? The number of mailboxes hosted is not directly correlated to the F5 device needed to support the users.



    For example, two customers can have the same number of mailboxes hosted - let's say 130,000 - but one expects 10% concurrency vs another expects 50% concurrency.



    Furthermore, based upon which access method is used for Exchange, the overall traffic generated by the client is different - OWA interface, for instance, is MUCH richer in Exchange 2010 than it is in 2003 or even 2007 - so from pure HTTP perspective, a single OWA user is going to generate a lot more traffic and requests/sec using OWA 2010 than they did with older versions.



    Even for RPC-only deployments in Exchange 2010, all traffic is nowgoing to CAS array, vs in 2003 and 2007 RPC traffic was going directly to the mailbox server - and since F5 is load-balancing CAS array, it means that all RPC traffic is going to go through F5.



    Sitting down with your local F5 team to best understand the requirements and nuances is the best recommended approach - and you are always welcome to post specific questions on this forum as well.


  • With over 250,000 Exchange mailboxes and a multitude of F5 products usage patterns have indeed changed with the changing Exchange versions.



    Exchange 2003 is hardly the best comparison to Exchange 2010, but when dealing with 10,000 mailboxes at your largest site a 6900 model is complete overkill even if loading all of the bells and whistles. We maintain over 600k concurrent Exchange connections mostly RPC/HTTPS in a 35 node CAS Array on a 6900, SSL Offloading, irules, etc and the the unit is bored.




    I would indeed engage your local F5 rep but IMHO a 1600 pair for your small site and a 3600 pair for your large site will likely give you the performance you need.


  • Thank you Casey. I already have a dialog open with our SE, but my intent with this question was really to get a sense of some numbers from other F5 customers. It's fine to speak with F5 about this, but they have a financial interest in what hardware we purchase. I like to hear what other customers are doing since they aren't motivated by the same incentives.



    If anyone else has feedback on their usage numbers, I'd love to hear them!