This Knowledgebase article provides an overview of Neverfail Cascade.
Neverfail Cascade is a customized, field-engineered solution that complements Neverfail Heartbeat and provides Disaster Recovery by replicating the protected data set from the Neverfail server pair to a Tertiary server, which is typically at a remote location. This configuration is often desirable in situations where one might desire a local High Availability pair plus a remote Disaster Recovery server. The following considerations are important when considering a Neverfail Cascade implementation:
- Neverfail V5.0.2 is the final version that supports Neverfail Cascade.
- Neverfail Cascade can ONLY be used in conjunction with Neverfail for Exchange or Neverfail for SQL Server.
- As Neverfail Cascade is a customized, field-engineered solution, it can only be installed and configured by Neverfail staff.
The Tertiary server is "fed" from the Secondary server whenever the Secondary server is in Passive mode. Consequently, replication to the Tertiary server will stop if the Secondary server becomes Active, for instance in the case of a failover or switchover.
- Switching back from an Active Secondary server to a Passive Primary server will require the Tertiary server to be completely re-synchronized with data from the Secondary following the switchback process.
- The Tertiary server provides no monitoring of the High Availability pair, and therefore all failovers to the Tertiary server must be initiated manually.
- Following a failover to the Tertiary server, no automated processes exist for restoring data/service back to the High Availability pair; however, a set of documented manual steps can be provided as guidance.
The Tertiary server can either function as:
- A simple data store (easy to setup, longer to failover) - in this case, the Tertiary server must simply have the same OS version and service pack level as the High Availability pair.
- A clone of the High Availability pair (more complex to setup, quicker to failover) - in this case, all servers must be running Windows 2003 SP1.
A Neverfail SCOPE Professional, SCOPE Enterprise Data Collector, or SCOPE Data Collector service analysis of application load and network bandwidth is essential. Neverfail Cascade is not recommended for applications under substantial load, due to the dependency on high bandwidth to the Tertiary server. A minimum bandwidth of 10 Mbit between the High Availability pair and the Tertiary server is highly recommended.
Neverfail Heartbeat V5.0.2 and prior