High Availability (HA)

HCL 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 HCL 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 HCL Traveler server as a single point of failure.

Additional single points of failure should be eliminated for a complete highly available system:
  • Mail Servers

    Mail servers should be clustered. In the event that a user's mail database becomes unavailable due to a server failure, HCL 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, clustered or run in an active-active configuration so that in the event of a database server failure the Traveler servers in the HA pool can reconnect to a secondary database server. The main requirement for Traveler is that all Traveler servers in the HA pool must connect to the same physical database server. When fail over occurs all Traveler servers in the HA pool must fail over to the same secondary database server. Running a Traveler HA pool where the Traveler servers are connected to different physical database servers is not supported and may result in bad user experiences including missing data on their mobile devices and/or frequent re-syncing of data. For specific information about how to setup your enterprise database with fail over, see your database providers documentation.

  • 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.