Determine Connection Priorities

  • Article

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Connection priorities control the sequencing of the initial synchronization that occurs when you add a new member to a replica set or when you perform a nonauthoritative restore. By changing connection priorities, you can control which inbound partners go first based on resource considerations. (A server’s inbound partners, also known as upstream partners, are those servers from which the new or recovered member can receive replicated content.) For example, you can specify that a new member first synchronize with a partner:

  • Across a high-bandwidth network connection.

  • That has low server activity.

  • That has the most up-to-date files.

You configure connection priorities by using the three priority levels in the Distributed File System snap-in:

  • High. All connections marked High must successfully synchronize before FRS attempts to synchronize medium-priority connections.

  • Medium. At least one medium-priority connection must successfully complete an initial synchronization before FRS attempts to synchronize any low-priority connections. FRS attempts to synchronize all connections in the medium-priority level, but only one must be successful before FRS attempts to synchronize low-priority connections.

  • Low. The default connection priority is low. For these connections, FRS attempts to synchronize one time, but any failure does not delay other synchronization attempts. If no medium- or high-priority connections exist, at least one low-priority connection must succeed before FRS considers the initial synchronization operation complete. If medium- or high-priority connections exist, none of the connections in the low-priority class needs to succeed for FRS to consider the initial synchronization operation complete.

Important

  • Connection priorities are used for initial synchronizations only on custom topologies. If you use a ring, hub and spoke, or full mesh topology, connection priorities are used only on reinitialization during a nonauthoritative restore operation.

When evaluating your topology to determine connection priority, identify the following details for each replica member:

  • All inbound connections

  • The speed of those connections

Based on this data, determine which connection priority to assign to each inbound connection. The following guidelines will assist you in choosing the appropriate connection priority:

  • Use medium priority or high priority only for high-bandwidth connections.

  • If you plan to create a high-priority connection, note that if this connection fails, no other synchronization takes place for lower-priority partners until all high-priority connections have succeeded.

  • Use low priority for low-bandwidth or unreliable connections.

Note

  • Keep in mind that after the initial synchronization, connection priorities are ignored until you need to perform a nonauthoritative restore to recover a failed replica member.

For an Excel spreadsheet to assist you in documenting connection priorities, see "FRS Configuration Worksheet" (Sdcfsv_2.xls) on the Windows Server 2003 Deployment Kit companion CD (or see "FRS Configuration Worksheet" on the Web at https://www.microsoft.com/reskit).

Figure 2.14 illustrates an organization’s planned topology. The letters A through C represent inbound connections. The hub servers are connected by a high-bandwidth network connection, and two of the hub servers connect with branch servers by using low-bandwidth network connections.

Figure 2.14   Sample FRS Topology

Sample FRS Topology

In this topology, the administrator assigns connection priorities as follows:

  • "A" connections use medium priority because the hubs are connected by high-bandwidth connections and the hub servers are expected to be up to date.

  • "B" and "C" connections use low priority because the branch servers connect to the hubs across a low-bandwidth network.

When the hub servers in this example are deployed, Hub1 will be the initial master. Because the "A" connections are marked as medium priority, the two other hub servers will not attempt replication with the branch servers until initial replication completes with at least one other hub server.

The administrator specifies connections "B" and "C" as low priority because the branch servers have low-bandwidth network connections. In the event of a nonauthoritative restore for any of the hubs, using low priority causes the repaired hub server to replicate first from other hubs before replicating with the branch servers.

Note

  • To increase the availability of data, the administrator can place multiple servers in each branch. If the servers in the branch use high-bandwidth connections to each other, the administrator can set medium priority for those inbound connections. That way, if one of the branch servers fails and is later restored, it will first attempt to replicate with a local branch server before replicating from the hub server across a slow network connection.