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Determining optimal number of Hybrid servers RRS feed

  • Question

  • Hi,

    I want to know what should be the optimal number of Hybrid Exchange servers when planning to migrate from On premise Exchange to O365. I have previously worked with only 4 servers for 60K + mailboxes. I am having a customer who are planning to have 10+hybrid servers for only 25K mailboxes. Isn't that a bit high? Any suggestions?


    Regards BM

    Thursday, November 21, 2019 8:01 PM

Answers

  • Hi,

    I want to know what should be the optimal number of Hybrid Exchange servers when planning to migrate from On premise Exchange to O365. I have previously worked with only 4 servers for 60K + mailboxes. I am having a customer who are planning to have 10+hybrid servers for only 25K mailboxes. Isn't that a bit high? Any suggestions?


    Regards BM

    Theres really no such thing as a hybrid server. You simply use the existing CAS role servers as your "hybrid" servers and if that number is working now on-prem, it will work fine in hybrid mode.
    Thursday, November 21, 2019 10:16 PM
    Moderator
  • For a restricted Exchange environment where nothing is exposed to public world be it OWA, EWS, ECP etc, you are saying good practice is to expose the on premise Exchange environment for O365 migration. The servers do not even have a public cert and being worked on by internal cert. EWS/MRS, Autodiscover needs to be enabled in the existing on premise exchange servers which are hosting mailbox databases for O365 migration. Won't you agree?

    Regards BM

    Well, thats a different question then isnt it? Thats not a technical reason though, thats a business decision. If you have an environment like that and want to only expose a specific number of servers to Office 365, you can certainly do that. But in those cases, there is no set number and it has nothing to do with load or traffic. In those scenarios, have maybe at least 2 servers used for the hybrid endpoints, but note , most of the work is still being handled by the mailbox servers that hold the actual mailboxes, not the "Hybrid servers"
    Monday, November 25, 2019 2:16 PM
    Moderator

All replies

  • Hi,

    I want to know what should be the optimal number of Hybrid Exchange servers when planning to migrate from On premise Exchange to O365. I have previously worked with only 4 servers for 60K + mailboxes. I am having a customer who are planning to have 10+hybrid servers for only 25K mailboxes. Isn't that a bit high? Any suggestions?


    Regards BM

    Theres really no such thing as a hybrid server. You simply use the existing CAS role servers as your "hybrid" servers and if that number is working now on-prem, it will work fine in hybrid mode.
    Thursday, November 21, 2019 10:16 PM
    Moderator
  • You can get idea by using Exchange deployment assistant here,

    https://assistants.microsoft.com/

    https://docs.microsoft.com/en-us/Exchange/mail-migration-jump

    Friday, November 22, 2019 4:46 AM
  • But we don't want to disrupt our existing on prem exchange environment. There will be additional migration, smtp and autodiscover traffic. So we want dedicated cas/mbx servers to take the load which are not hosting the on prem mailbox databases. So we are building additional Hybrid Exchange servers, natting them to a public IP/FQDN (hybrid.mydomain.com), opening firewall ports between o365 and those boxes. I have worked with fewer previously. So wanted to know how many those dedicated servers will be optimal. 

    Regards BM

    Friday, November 22, 2019 5:07 AM
  • But we don't want to disrupt our existing on prem exchange environment. There will be additional migration, smtp and autodiscover traffic. So we want dedicated cas/mbx servers to take the load which are not hosting the on prem mailbox databases. So we are building additional Hybrid Exchange servers, natting them to a public IP/FQDN (hybrid.mydomain.com), opening firewall ports between o365 and those boxes. I have worked with fewer previously. So wanted to know how many those dedicated servers will be optimal. 

    Regards BM

    There is no number that is optimal. If you have sized your existing org correctly, why  do you think it wont be able to handle hybrid mode? There will not be any increase in autodiscover or SMTP traffic that will be of any consequence. If you were migrating from 2013 > 2016, would you add more 2013 servers to handle the mailbox moves? No. This is is no different. I dont see the need or point of adding special servers, quite frankly. Really a waste of resources and time. 

    The existing servers will still be doing all the work since thats where all the mailbox are. You gain nothing by adding more servers for hybrid.

    https://docs.microsoft.com/en-us/exchange/server-roles

    When configuring a hybrid deployment in an Exchange 2016 organization, you don't have to install any additional Exchange servers in your existing Exchange organization. Your Mailbox servers coordinate communications between your existing Exchange 2016 organization and the Exchange Online organization. This communication includes message transport and messaging features between the on-premises and Exchange Online organizations. We highly recommend installing more than one Exchange server in your on-premises organization to help increase reliability and availability of hybrid deployment features.


    Friday, November 22, 2019 12:12 PM
    Moderator
  • Thanks! but ideally whatever the migration project i worked, even with Microsoft. Everywhere separate Exchange servers were built where Hybrid CW was run. Those servers were dedicated for migration, SMTP and autodiscover flow. Even when the on premise mailbox/cas servers were adequate. 

    Regards BM

    Friday, November 22, 2019 1:30 PM
  • Thanks! but ideally whatever the migration project i worked, even with Microsoft. Everywhere separate Exchange servers were built where Hybrid CW was run. Those servers were dedicated for migration, SMTP and autodiscover flow. Even when the on premise mailbox/cas servers were adequate. 

    Regards BM

    Then they were doing it wrong :)

    Seriously, if someone thinks creating hybrid servers somehow moves traffic to those servers and decreases the load, they dont understand how Exchange works.

    Saturday, November 23, 2019 12:29 AM
    Moderator
  • For a restricted Exchange environment where nothing is exposed to public world be it OWA, EWS, ECP etc, you are saying good practice is to expose the on premise Exchange environment for O365 migration. The servers do not even have a public cert and being worked on by internal cert. EWS/MRS, Autodiscover needs to be enabled in the existing on premise exchange servers which are hosting mailbox databases for O365 migration. Won't you agree?

    Regards BM

    Monday, November 25, 2019 2:08 PM
  • For a restricted Exchange environment where nothing is exposed to public world be it OWA, EWS, ECP etc, you are saying good practice is to expose the on premise Exchange environment for O365 migration. The servers do not even have a public cert and being worked on by internal cert. EWS/MRS, Autodiscover needs to be enabled in the existing on premise exchange servers which are hosting mailbox databases for O365 migration. Won't you agree?

    Regards BM

    Well, thats a different question then isnt it? Thats not a technical reason though, thats a business decision. If you have an environment like that and want to only expose a specific number of servers to Office 365, you can certainly do that. But in those cases, there is no set number and it has nothing to do with load or traffic. In those scenarios, have maybe at least 2 servers used for the hybrid endpoints, but note , most of the work is still being handled by the mailbox servers that hold the actual mailboxes, not the "Hybrid servers"
    Monday, November 25, 2019 2:16 PM
    Moderator
  • Thanks Andy.

    Regards BM

    Tuesday, November 26, 2019 2:34 PM
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    Joyce Shen


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    Wednesday, November 27, 2019 9:13 AM
  • A brief summary of this post so that other forum members could easily find useful information here:

    [Determining optimal number of Hybrid servers - summary]

    Request/Expectation: 
    What should be the optimal number of Hybrid Exchange servers when planning to migrate from On premise Exchange to O365.

    Solution Summary: 
    There is no number that is optimal.
    You simply use the existing CAS role servers as your "hybrid" servers and if that number is working now on-prem, it will work fine in hybrid mode.

    Friday, November 29, 2019 8:33 AM