User Guide

154 Administering ColdFusion Server
• No single point of failure
By distributing the load balancing and failover capabilities among multiple
servers in a cluster, as opposed to relying on only a single device, no individual
server failure will disable your application.
Considerations
Consider the following issues when evaluating software-based solutions for your
environment:
• Differences among feature sets
Not all software-based clustering solutions are the same in terms of capabilities
and features. For instance, some have no automatic failure detection,
notification, or IP address assumption, and others have significantly delayed
detection. Some let you configure load thresholds to enable preventive
measures, some don’t. Determine your scalability and failover needs in advance
and pick your solution accordingly.
• Platform constraints
Determine if the software solution you are considering will be available on your
platform or operate with your preferred Web server. If reviewing data sheets
and other marketing collateral from vendors, make sure that the robust features
you want are available on the platform you need.
• Level of complexity
Some software-based clustering solutions have relatively low complexity.
Others introduce a higher level of complexity because of the features offered,
the amount of initial configuration and subsequent administration, or the
amount of integration that needs to occur between other systems and devices.
Combining hardware and software clustering solutions
Instead of having to choose either a hardware solution or a software solution, another
possibility is to combine both types of clustering choices. Combining hardware and
software solutions will certainly provide the greatest scalability and availability
capabilities for your site. Additionally, a combined solution is an attractive option if
your organization has already invested in one but is looking for more comprehensive
coverage. Having the flexibility to integrate hardware with software means that your
organization won’t necessarily have to absorb a capital loss on a previous technology
investment if you decide to purchase additional clustering technology.
However, as already discussed, not all hardware or software solutions are equal. Many
have different features and capabilities, and not all hardware and software integrate
well together. Be sure to investigate thoroughly when purchasing additional
technology to augment your current solution.
For a visual representation of hardware and software clustering solutions working
together, see “Hardware-based clustering solutions” on page 150.