MailEnable Enterprise Guide
Cluster Management / Windows licensing for cluster setup
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    Windows licensing for cluster setup
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    MailEnable clustering uses Network Shares (UNC Shares) to allow member servers to access the message store and underlying configuration. When a server is established as a cluster controller (backend server), MailEnable creates a UNC share that is configured to "permit the maximum allowed number of users" to access the share.

    However, even though MailEnable is configured to have the "maximum number allowed" users, the actual number of users permitted to access the server varies according to Windows licensing.

    For a server, the maximum number of users is the number of users for which you have purchased Windows licenses.  For an Windows workstation there is a built-in limit of 10 simultaneous users for a shared resource (e.g. UNC share).

    When an application or service, such as MailEnable attempts to access a share that already has the maximum number of users, an error is generated and the connection is refused.

    This error is typically formatted as “No more connections can be made to this remote computer at this time because there are already as many connections as the computer allows.”

    When establishing a MailEnable cluster, carefully consider the licensing policy of the server that is hosting the message store and configuration files.

    Ensure that you have purchased adequate Windows licenses to sustain connections from member servers to the backend storage server. At a minimum, this will require licenses for member servers as follows:

    1. License for each member server for the IME_ADMIN (Web Mail and Web Administration service account) user.
    2. License for each member server account that is used to administer the server. e.g.: Administrator or any other privileged account that uses the MMC on a member server.

    e.g.: If there was 1 backend server and two front-end servers, the backend server would need to sustain or be licensed for at least 4 connections (above whatever connections are used by other applications or server functions).

    The means of configuring Windows licenses varies depending on the Windows platform/version being used. Consult the respective Windows documentation to clarify this.