Capacity Planning for Group Chat Server

Single-Server Topology

The minimum configuration and simplest deployment for Group Chat Server is a single-server topology. This topology can support as many as 20,000 users. It requires a server to run Microsoft Lync Server 2010, a Group Chat Server, a server to host the Group Chat database, and workstations to host Microsoft Lync 2010 Group Chat. If compliance is required, you need an additional server to host the Compliance service and an additional database to store the compliance data. The compliance database can be collocated with the Compliance service.

The following figure shows all the components of the single-server topology with the optional Compliance service.

Single Group Chat Server

Multiple-Server Topology

To provide greater capacity and reliability, you can deploy a multiple-server topology, as described in Planning for Group Chat Server. The multiple-server topology can include as many as three Group Chat Servers, each of which can support as many as 20,000 users, for a total of 60,000 users. A multiple-server topology is the same as the single-server topology except that multiple servers host Group Chat Server. Multiple Group Chat Servers should reside in the same AD DS domain as Lync Server and the Compliance service.

The following figure shows all the components of a multiple-server topology with multiple Group Chat Servers, the optional Compliance service, and a separate compliance database.

Multiple Group Chat Servers

In a three-server Group Chat Server deployment, where 60,000 users can be simultaneously signed in to and using Lync 2010 Group Chat, the load is distributed evenly at 20,000 users per server. If one server becomes unavailable, the users who are connected to that server will lose their access to Group Chat Server. The disconnected users will be automatically transferred to the remaining servers until the unavailable server is restored. Depending on the amount of Group Chat traffic on the network, this transfer can take a few minutes or as long as an hour. Because each of the remaining servers might be hosting as many as 30,000 users, we recommended that you restore the unavailable server as quickly as possible to avoid performance issues.

The load on the Group Chat Servers is balanced by the Lookup service. Group Chat Servers cannot be located behind a hardware load balancer. If the load becomes unbalanced after a server becomes unavailable, the Lookup service will rebalance the load when clients sign in and out, but it will not attempt to balance existing connections.

Planning Your Maximum Capacity for Group Chat Server

Use the following sample table to determine the number of users you will be able to support.

Group Chat Server Maximum Capacity Sample

In the preceding sample, the plan is to support the maximum number of users Group Chat Server allows: three servers/instances of the Channel service and 20,000 users per server, for a total of 60,000 active users.

Capacity Planning for Managing Chat Room Access

The following sample table can help you plan for managing chat room access in Group Chat Server.

Managing Chat Room Access Sample

In the preceding sample, when you deploy the Group Chat Servers according to the recommended guidelines, they can handle up to 60,000 active users across a three-server pool with compliance enabled.

This sample shows chat rooms categorized as small (30 active users at any given time), medium (150 active users), and large (12,000 active users). The number of chat rooms of a certain size is computed based on the total number of:

• Active users in the system

• Active users in chat rooms of the given size

• Chat rooms of the given size that a single user joins

You can modify the italic numbers in the previous table to estimate how many chat rooms of a certain size will be created in the system and the rate of outbound chat messages that the system is likely to generate. In the sample, where there are 60,000 active users in the system, if each user simultaneously joins 12 small, 2 medium, and 2 large chat rooms, there will be 24,000 small, 800 medium, and 10 large chat rooms created in the system.

For each chat room, the preceding capacity planning table specifies the number of access control entries that are associated with the chat room, including entries that are inherited from parent categories and entries that are assigned directly to the chat room. You can control access to individual chat rooms by using access control lists (ACLs). You can also control access at the category level. In an ACL, an individual access control entry can be either a user group—for example, a security group, distribution list, or federated user group—or a single user. You can define access control entries for chat room managers, presenters, and members.

For planning purposes, you must estimate the percentage of chat rooms that will be managed by assigning user groups instead of individual users. The data in the preceding sample assumes that the ACLs consisting of 50% of small chat rooms, 50% of medium chat rooms, and 50% of large chat rooms are made up exclusively of user groups, and the remaining chat rooms are made up of individual users.

In the preceding sample, the ACLs for the manager group, the presenter group, and the scope of a chat room category are constant across all chat room sizes. The sample assumes that there are six access control entries per chat room in each of these lists.

Capacity Planning for Managing Chat Room Access by Invitation

You can use the following capacity planning table to compute the number of invitations that Group Chat Server creates and stores in the Group Chat database when it is configured to send invitations. You manage invitations from the Chat room settings page either in the Microsoft Lync Server 2010, Group Chat Admin Tool or Group Chat Server client (Group Chat).

The sample data in the following table assumes that, on the Chat room settings page for 50% of all chat rooms, the Invitations option is set to Yes, and the chat rooms are operating at full capacity.

Chat Room Access by Invitation Sample

Group Chat Server Performance User Model

The following table describes the user model for Group Chat Server. It provides the basis for the capacity planning requirements and represents a typical organization with 60,000 concurrent users.

Group Chat Server Performance User Model