Unix Backup and Recovery

Step 1: Define (Un)acceptable Loss

A disaster recovery plan is an insurance policy. If you’ve ever read anything about backups, you’ve heard that before. I would like to extend that analogy. Consider your car insurance policy. All insurance policies in the United States start with PIP, or personal injury protection. That way if you hit someone and get sued, you are protected. You can then add coverage for collision, personal property, emergency roadside assistance, and rental car coverage. These additional layers of coverage are called riders. Just like your car insurance policy, disaster recovery plans may include optional riders. You simply need to decide the types of riders that your company needs, or can afford. How do you do this? You have to look at the potential losses that your company will suffer if a disaster occurs and decide which ones are acceptable or unacceptable, as the case may be. You then select the riders that will protect you against the losses that you have decided are unacceptable. (This analogy is discussed in further detail in Chapter 2.)

You need to make the same kind of decisions on behalf of your company. If it is unacceptable to lose a single day’s worth of data when a disaster happens, then you need to send your volumes to an off-site storage vendor every single day. You must decide what kind of losses your company is not willing to accept, and then insure against those losses with your disaster recovery plan. You cannot design a disaster recovery ...