Topic Last Modified: 2014-03-14

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Planning for the Deployment of Front End Pools

In Lync Server 2013, Front End pool architecture has changed, and these changes affect how you should plan and maintain your Front End pools.

We recommend that all your Enterprise Edition Front End pools include at least three Front End Servers. In Lync Server, the architecture of Front End pools uses a distributed systems model, with each user’s data kept on three Front End servers in the pool. For more information about this new architecture, see Topology changes.

If you do not want to deploy three Enterprise Edition Front End Servers and want high availability and disaster recovery, we recommend you use Lync Server Standard Edition and create two pools with a paired backup relationship. This will provide the best high availability and disaster recovery solution with only two servers. For more information, on high availability and disaster recovery topologies and features, see Planning for high availability and disaster recovery.

Planning for the Management of Front End Pools

For pools that contain three or more Front End Servers, follow these quidelines:

  • When you start the pool for the first time, be sure to start at least three of the Front End Servers.

  • When you move users to the pool for the first time, be sure at least three of the Front End Servers are running.

  • If you establish a pairing relationship between this pool and another pool for disaster recovery purposes, then after establishing that relationship you must be sure this pool has three Front End Servers running simultaneously at some time to properly synchronize data with the backup pool. For more information on pool pairing and disaster recovery features, see Planning for high availability and disaster recovery.

For a Front End pool to be functional, a certain number of Front End Servers in the pool need to be up and running, as shown in the table later in this section. When you plan upgrade and maintenance of a pool, you must keep this in mind. Overall, for upgrades of Front End Servers, we recommend you upgrade one server at a time. Bring one server down, apply the upgrade, then bring that server back up before upgrading another server. For detailed instructions for upgrading a Front End Server, see Upgrade or Update Front End Servers.

Total number of Front End Servers in the pool Number of servers that must be running for pool to be functional

1-2

1

3-4

2

5-6

3

7-8

4

9-10

5

11-12

6

If the number of servers running falls below the functional level as shown in this table, the remaining servers in the pool go into survivability mode, and you will see the following message in the event log: Local Pool Manager has been disconnected from Pool Fabric Manager. (Id: 32163). After five minutes, if the number of running servers is still below the threshold level, the remaining servers in the pool will stop all Lync Server services, and the following messages will be in the event log: Pool Manager failed to connect to Fabric Pool Manager (id: 32170) Server is being shutdown because fabric pool manager could not be initialized (id: 32173)

Note:
Because Lync Server uses the Primary SQL database as Witness, if you shut down Primary SQL and switch to the Mirror copy, and shut the number of FE servers listed in the “Number of servers that must be running for pool to be functional” column of this table, the entire FE Pool will go down. For more information, see Database Mirroring Witness.

Changing a Front End Pool’s Configuration

Whenever you add Front End Servers to a pool, or remove them from the pool, and then publish the new topology, follow these guidelines:

  • After the new topology has been published, you must restart each Front End Server in the pool. Restart them one at a time.

  • If the entire pool has been down during the configuration change, then run the following cmdlet after the new topology is published:

    Copy Code 
    Reset-CsPoolRegistrarState -PoolFQDN <PoolFQDN> -ResetType ServiceReset

If a Front End Server fails and is unlikely to be replaced for a few days or more, remove the server from the topology. Add the new Front End Server to the topology when it is available again.

Front End Pools with Two Front End Servers

We do not recommend deploying a Front End pool that contains only two Front End Servers. If you do ever need to deploy such a pool, follow these guidelines:

  • If one of the two Front End Servers goes down, you should try to bring the failed server back up as soon as you can. Similarly, if you need to upgrade one of the two servers, bring it back online as soon as the upgrade is finished.

  • If for some reason you need to bring both servers down at the same time, do the following when the downtime for the pool is finished:

    • The best practice is to restart both Front End Servers at the same time.

    • If the two servers cannot be restarted at the same time, you should bring them back up in the reverse order of the order they went down.

    • If you cannot bring them back up in that order, then use the following cmdlet before bringing the pool back up:.

      Copy Code 
      Reset-CsPoolRegistrarState -ResetType QuorumLossRecovery -PoolFQDN <FQDN>