When deciding to deploy IBM Lotus Notes Traveler version 8.5.3 Upgrade Pack 1, a number of questions should be asked in regards to using the high availability (HA) option or the stand-alone option. By default, the installation of 8.5.3 Upgrade Pack 1 is a stand-alone server. It is not until you want to configure Lotus Notes Traveler for HA that an enterprise database and a 'front-end' IP sprayer are required.
The two main influencing factors to choosing a stand-alone server versus an HA Lotus Notes Traveler implementation are:
- The number of devices Lotus Notes Traveler is to service
- The need for continuous availability or fail-over capability if a Lotus Notes Traveler server instance becomes unavailable.
Other factors are also discussed after we address these main two concerns.
Number of devices
Lotus Notes Traveler 8.5.3 Upgrade Pack 1 has improved the server capability to manage memory and data in the servers. With this improvement, the server performs faster and maintains better data organization in the Lotus Notes Traveler databases. These are either the local derby databases that are used by Lotus Notes Traveler in stand-alone mode, or the enterprise databases that are used in the HA mode. The improvement was largely due to the improvement, and refactoring of many of the SQL queries that are used, and adjustments to the tables that are contained in the Lotus Notes Traveler databases. Because of these important factors, if your current implementation of Lotus Notes Traveler is providing service for 2,000 devices or less, then a stand-alone server with 8.5.3 Upgrade Pack 1 (of the correct specification) would be sufficient if you do not need your Lotus Notes Traveler server to be highly available.
If you plan to support more than 2,000 devices, using the HA environment is your best option. A single Lotus Notes Traveler 8.5.3 Upgrade Pack 1 server in an HA configurationcan service up to approximately 2,500 devices on a single server. For any additional devices above this number, another server is required to handle the load. A single HA server pool (consisting of multiple Lotus Notes Traveler servers, all configured in HA mode) can support approximately 10,000 devices. The basic rule of thumb is that the number of servers required in a Lotus Notes Traveler HA server pool is 1 + the number of servers needed to serve the load. For example, if you were to implement an environment that was intended to serve 5,000 users, you would need 3 Lotus Notes Traveler servers. The additional server is required so that if one of the servers in the pool failed, all of the devices can still be serviced by the remaining servers in the pool without degrading the quality of the service. Note that all of the servers in a HA pool are always used in normal circumstances so the additional server is utilized all of the time.
System availability consideration
If you wish to ensure that the Lotus Notes Traveler solution has continuous availability, then the HA option is the solution that must be used.
If you are implementing a HA solution you need to ensure that all of the components that make up the end to end Lotus Notes Traveler server are also high availably. As such the other aspects of the solution that need to be considered and have a high availability solution of their own include:
- A HTTP/IP Sprayer or load balancer server
- A Lotus Domino mail server (for example, use Lotus Domino clustering)
- A high availability solution for the enterprise database
The other considerations of using an HA solution include :
- Server resource constraint:
If your servers has a maximum of 8 GB memory only, the HA solution allows you to have multiple severs. With multiple servers you can handle a higher load with fewer devices on each server. Thus, you are able to service more devices with more machines when the machines are restricted on the resources they are allotted. This is more common in a VM environment.
- Network constraint:
If the internal network speed is not fast, or bandwidth is a limitation, consider the stand-alone solution if you do not need a HA solution according to the first two points described in this section. In a stand-alone configuration, all the resources are local and there is no traffic from the HTTP/IP Sprayer to the Lotus Notes Traveler server to the enterprise database server and back within the network.
What does IBM do internally?
At the time of writing, the IBM internal implementation of Lotus Notes Traveler is comprised entirely of stand alone Lotus Notes Traveler servers.