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Exchange 2010 - Do I need separate rolls on separate servers?

Discussion in 'Software' started by jiggy, Oct 11, 2011.

  1. jiggy

    jiggy Nibble Poster

    We're a small organisation (by head count at least) and are migrating Exchange from 03 (just a single server) to 2010. We have approx 130 people and send out at most 5000 emails per day total. We have about 20 various iphone / android devices. Lastly we wont be growing in headcount at all by any sizable amount.

    I am going to put a DAG in but I just dont know if I need to separate out the CAS / HT etc roles or if I can have them all on the same box without any problems.

    My thoughts are either 2 servers holding all the roles (1 at our main site, 1 at our backup with the DAG between these) or 2 servers at each site with the mailbox role on 1 and all other roles on the other.

    All our mail is routed through an external provider so very little spam makes it to our front door so Im not to worried about our servers getting overloaded with spam.

    What do those who have done this before think? 1 server at each site holding all the roles or 2 servers at each site with the roles split?
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  2. Phoenix
    Honorary Member

    Phoenix 53656e696f7220 4d6f64

    well the support problem is this
    you cant use NLB for CAS on the same server you use DAG on
    so, if you use two servers for DAG, you need dedicated CAS/HUB servers
    that said, your environment sounds a little different

    you are looking at two AD sites (Active and DR)
    so you could have two servers with all roles, and NO NLB between CAS (you would not do this for a multi site deployment anyway)
    you will however have to factor in how to access the secondary cas/hub in the event of primary site failure
    and assuming you were stretching the dag offsite for resiliency, you would still need a CAS/HUB located there anyway

    so sounds like two servers, HUB/CAS/MB on each, with a DAG between the two
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  3. Shinigami

    Shinigami Megabyte Poster

    As Phoenix said, NLB won't work for multi-role servers participating in a DAG.

    The current Microsoft recommendation is to go for less powerful servers which host all roles as this "spreads the love" so to speak (the thinner you spread your mailbox distribution, the fewer the impacted users if servers are lost). And by doing multi-roles, you are always providing each role as a fully functioning entity for the users being hosted locally by the server. It keeps costs down, maintains a standard configuration, and simply makes things simple.

    A Hardware Load Balancer these days costs very little... DNS Round Robin is an alternative, but get an HLB if you can. So yes, two multi-role servers is what I too would deploy in your situation.

    Learn to use the Exchange storage calculator to determine the actual server configuration. 130 users sending 5000 mails, probably also means that they receive 5000 or more mails a day. Let's round this up to 13,000 mails sent and received per day (total). That's 100 mails per user which gives a mail profile of 6MB required per user. Thus, each mailbox server needs 1GB of RAM just for treating mail. Throw in the server side requirements (OS overhead), the RAM requirements per role (CAS/Hub) and I'd say you can probably get by with servers that have 8GB of RAM each (assuming it's a multi-role with CAS+Hub+MBX).

    If it's a physical server, calculate the CPU overhead in megacycles, and any current server would have the processing power needed to service these users. If you're virtualizing, a single core might even work (but it also depends a little on antivirus products, additional agents and connectors, the actual size of mails and number of DB's you want to deploy, etc...).

    But here I am talking out loud again...
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  4. dmarsh

    dmarsh Terabyte Poster

    I prefer to place a jam roll on one server and sausage roll on the other, I find it helps a immeasurably !
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  5. craigie

    craigie Terabyte Poster

    Also dont forget that you wil need a File Share Witness at a third site for the DAG failover to work.
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  6. Shinigami

    Shinigami Megabyte Poster

    He'll need a FSW to maintain Quorum votes, and if there's a chance that the network link between the two servers is lost, he'll also benefit from DAC and Alternate Witness. Typically this is used for DR situations but requires careful planning and testing as it requires administrator intervention to work properly.

    In his case, as he has a backup site and will probably run an Active/Passive configuration, the use can be warranted.
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  7. jiggy

    jiggy Nibble Poster

    great, thanks for all the feedback guys. Yup sausage rolls are the best :oops:

    2 servers with all "roles" sounds like the way to go then. Everything will be on VMWare and throwing 8 gigs RAM at each machine is not a problem, more can easily be done. I am lucky enough to work somewhere where money isnt really a problem if it is justified to spend it so hardware NLBers should be ok.

    Off to read about file share witnesses, not sure what that is about.

    Thanks again.
    Certifications: MCSE
    WIP: ABC's

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