Failover & Disaster Recovery [closed]

问题:

What's the difference between failover and disaster recovery?

回答1:

Failover: When one machine fails, another machine (usually in the same location) takes over and resumes service

Disaster recovery: When Godzilla destroys your data center, you do have alternative locations to keep providing your service and protocols/means for the other location to know how to keep delivering the service

Depending on the particular needs of each service, disaster recovery might just be a backup tape in a safe in a different location. In other words, it's just having a defined protocol to recover from disaster. Likewise, failover might just be having a spare backup machine which makes you go to the data center for it to take over the place of the failed one, that is, having a defined protocol about what to do in case of machine failure.

Summing up, failover answers the question 'what do I do in case a single machine fails?', disaster recovery answers 'what do I do in case a disaster happens (fire, floods, war, ISP goes bankrupt, whatever)?'

High Availability Deployment Architecture

回答2:

Failover is more linked to backup procedure.

The main difference between the two, from the end client's point of view is the downtime.

• Failover is expected to have a low downtime (1 2 hours top)
• DR can have anything between 6 hours to a day or two.

The other difference is the nature of environments available after a failover or a DR.

• Failover means the end clients see nothing and can continue his activity (development or production management)
• DR should mean only production environment is back up. All development environments are down, or seriously degraded.

回答3:

Since a disaster (like 9/11) can completely destroy a datacenter, does it mean that DR is the processes of rebuilding everything for that datacenter?