Hot Site Backup

I am currently investigating the different ways in which it is possible to have two Online systems on two separate machines, where one machine is a backup up of the other. I am particularly interested to find out how people are going about solving this problem with existing configurations, especially where the two systems are located in different locations. (any details regarding implementation would be appreciated) I would appreciate it if you could let me have any information regarding existing strategies employed, tips etc. I will summarise the results I get. I have listed below the options which I have thought of and added what I consider to be the pros and cons for each scenario. 1. Mirrored Dual Ported Disks DESC A single set of disks are wired up to two separate machines PROS a. The systems are in sync on a write by write basis. CONS a. The machines have to be at the same location 2. Fast Recovery DESC Machine 'B' in fast recovery with logs being rolled forward from machine 'A'. PROS a. If automated then the two systems can be remote CONS a. The systems are out of sync by at least one log. 3. Two Phase Commit DESC a. Use Online-5.00's 2 phase-commit capability. Now any transaction which is performed on 'A' occurs at the same time on system 'B'. PROS a. Systems are up to date with each transaction CONS a. Existing applications have to be modified b. Online has to be upgraded if not verison 5.00 4. Hot Site Backup (aka Data Replication) DESC Feature available in version 6.0 CONS a. Not yet available b. Online has to be upgraded. regards /***************************************************************************** Simon Parker (simonp) Informix UK Systems Engineer tel : (0784) 249 859 uunet : simonp@informix.com ******************************************************************************/