Different Bet. Hot-backup, Redundant?

[ckchew666]

Hi,

Can anyone explain what is the different between Hot Backup, Cold Backup and Redundant?

Normally I heard of hot backup apply on PLC-5 and SLC 500. Primary is processing and when primary downs, secondary will take over the data and process.

For redundant, primary and secondary is running/processing in parallel. Normally heard of this when talking about CLX.

Correct me if I'm wrong. Thanks.

Regards,
CK Chew

 

[Bakerman]

In general (I say that because individual's interpretations do vary):

Hot Backup:

A single processor is controlling the process, there is a second processor in the system that is being routinely updated with information from processor #1 so that it may take over the process at any time.

Cold Backup:

Similar setup, but no automatic transfer of control. Most likely requires a human to activate the backup processor, update it, or even slide it into a rack/group/etc. Not much different than having a spare laying near the main processor.

Redundant:

Best setup. Two processors running in parallel to control the process. Both are 100% up to date, either one can control the process at any time. In some systems (Foxboro) the two processors actually share the process, so there is no "changeover" between the two. Absolutely no loss in processing time, seamless changover.

Does this help?