High Availability (HA)
IBM Traveler servers can be configured to use a shared enterprise database. This configuration is referred to as a High Availability (HA) pool.
In this configuration, all of the sync history and administration information for a device is stored in the enterprise database. This allows any server in the HA pool to be able to service requests from any user/device. A user's mail is monitored for changes only on one server in the HA pool. For maximum efficiency, all devices for a user are routed to the IBM Traveler server that is monitoring the mail for that user. In the event that a server becomes overloaded or unavailable, another server in the pool will takeover the responsibility for monitoring a user's mail and device requests will be rerouted. The advantage of this type of configuration is the ability to balance the load of requests amongst the pool of servers, seamless add capacity, as well as eliminate the IBM Traveler server as a single point of failure.
- Mail Servers
Mail servers should be clustered. In the event that a user's mail database becomes unavailable due to a server failure, IBM Traveler will switch to an alternate mail server in the cluster. For more information, see Domino mail clustering.
- Enterprise Database Servers
The enterprise database server can be mirrored, replicated, or clustered so that in the event of a database server failure, the servers in the HA pool can reconnect to the secondary database server. Using a High Availability database server configuration allows IBM Traveler devices to generally continue synchronizing without requiring a full recovery sync with mobile devices. Most enterprise database servers provide different configuration options with regards to how a database change made on the primary server is also made on the secondary database server. The larger the degree of synchronization, the greater the data protection will be, and the more impact to the overall response time of a device request. The less the degree of synchronization, the greater the chance that in the event of a failover scenario, some database changes are lost. This can result in a device recovery synchronization for some devices.
- IP Sprayer
An HA pool requires a front end service that can provide a single URL entry point and evenly spread requests across the HA pool. This typically can be provided by some form of an IP Sprayer. A redundant server should be employed to avoid the IP Sprayer becoming a single point of failure.