Computer Associates BABNWUP900NE6 Administration Guide - Page 50

Defining Storage-capacity Requirements Defining Storage-capacity Requirements So far, we have discussed factors that affect the speed with which backup and restore operations can be performed. But you also need to consider the volume of online data storage that you require. How Much Space Do You Need for Online Recovery Data? You need to figure out how much recovery data you need to store online, in your robotic libraries. Data that is used primarily for archival purposes or for recovery after a catastrophe can be stored offline in a repository or vault. It is unlikely to be needed quickly. But recent backup data generally has to be available in a robotic library so that users can easily locate and swiftly recover the most recent, intact copies of the files they are most likely to lose. To calculate the amount of recovery data you must store online, perform the following steps: 1. Estimate the size of an average, full backup. 2. Add the estimated size of an average incremental backup. 3. Multiply by the number of backup sets that your organization wants to have immediately available ("1" for the most recent, "2" for the two most recent, and so on). This is the amount of recovery data you need to keep online: recoverydata = (avgsizefull + avgsizeincrements) × numberbackupskept How Much Space Do You Need for Backed-up Data? You need to reserve online storage space for scheduled backup operations. To calculate this space: 1. Estimate the size of an average, full backup. 2. Add the average, percent growth of the data set during a typical, full backup cycle. 3. Add the estimated size of an average incremental backup. 4. Add the average percent growth of the data set during a typical, incremental backup cycle. 2-12 Administrator Guide