Best practices for High Availability (HA)

The following are best practices to consider when planning for a highly available HCL Traveler Server environment.

Avoid network latency between servers

Where possible for maximum performance, locate as much of the Traveler infrastructure in the same lab, even on the same switch if possible. Include Traveler servers, Domino mail Servers, enterprise database servers Servers, directory servers, proxy, firewalls and load balancers. Of course this isn't always practical. When distributing equipment across switches or labs, it is important to test the network speed between the locations. Network ping times of more than 50ms can impact the overall capabilities of the environment. When equipment is distributed, installing a dedicated network between labs can greatly improve performance and capacity. Never distribute Traveler servers in an HA pool as they rely heavily on server-to-server communication to manage users with multiple devices and devices that sync over multiple threads concurrently.

Avoid single points of failure

To reduce the impact of server failure and to optimize performance, put each component of HCL Traveler on its own server. For example, avoid hosting the mail servers and HCL Traveler on the same servers. In addition to using a Traveler HA environment to provide redundancy for the Traveler server itself, also consider implementing redundancy of other required components, by clustering the mail servers, providing redundancy in the firewall, proxy or load balancer, and so forth.

Plan for failover

Size the servers in the HA pool such that there is spare capacity to handle failover. For example, assume a server capacity of 2000 devices and a total population of 4000 devices. A two server pool will not be adequate, as one server cannot handle 4000 devices in the event the other server is taken offline. Therefore, to adequately handle the device load in the event of one server going offline, three servers are required.

Traveler servers cannot be deployed in an Active-Active configuration

The enterprise database server can be mirrored, replicated, clustered or setup in an active-active configuration, however the Traveler servers in a Traveler HA pool must all 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.