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Defining Exchange disaster recovery

Paul Robichaux Realtimepublishers

Depending on whom you ask, the definition for disaster recovery can range from restoring data from a backup to restarting operations at an alternative business continuance site. This chapter will use the Wikipedia definition, which

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defines disaster recovery as "The ability of an infrastructure to restart operations after a disaster."

You are reading tip #1 from "10 tips in 10 minutes: Fundamentals of Exchange Server disaster recovery," excerpted from Chapter 2 of the book The Definitive Guide to Exchange Disaster Recovery and Availability, published by Realtimepublishers.
Let's add to that definition by clarifying that disaster means an event that causes loss of data or interruption in services. The combination of these definitions gives us a good starting point for a discussion of disaster recovery, although there are some additional nuances that need to be explored before talking about technical means of implementing disaster recovery.

The first is how you know when you've successfully recovered from the disaster. There are two common metrics for recovery:

  • A recovery point objective (RPO) specifies the point in time at which your capabilities will return when recovery is complete. Let's say you do a daily full backup at 2 a.m. If you have a failure Tuesday at 8 a.m., your RPO will probably be 2 a.m. Tuesday; in other words, your recovery will succeed if you can recover the state of your Exchange data to that particular point in time.

  • A recovery time objective (RTO) specifies the maximum amount of time allowed for a recovery. For example, if your service level agreement (SLA) promises that you'll restore operations within six hours of a disaster, you have a six-hour RTO.

Although these metrics are clearly related, there are significant differences between them that become apparent as you start to consider how to reduce the RTO or move the RPO closer to the actual beginning of the outage. To shorten the interval between a failure and your RPO, you must make more frequent copies of your data with whatever protection mechanism you've chosen. To shorten the RTO, you need to take measures to increase the speed of your recovery. The remainder of this chapter will discuss both types of measures.


10 tips in 10 minutes: Fundamentals of Exchange Server disaster recovery

 Home: Introduction
 Tip 1: Defining Exchange disaster recovery
 Tip 2: How Exchange backs up data
 Tip 3: Choosing a backup type for Exchange
 Tip 4: Online vs. offline Exchange Server backups
 Tip 5: Basic Exchange backup and restore
 Tip 6: Exchange vendor snapshots and point-in-time copies
 Tip 7: VSS for Exchange
 Tip 8: Exchange Server replication
 Tip 9: Exchange design choices and issues
 Tip 10: Exchange disaster recovery planning

This chapter excerpt from the free e-book The Definitive Guide to Exchange Disaster Recovery and Availability, by Paul Robichaux, is printed with permission from Realtimepublishers, Copyright 2005. Click here for the chapter download or download all available chapters here.


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