Computer Associates BABWBR1151S38 Implementation Guide - Page 26

Storage Capacity Requirements Parallel Storage Operations (Multiple Streaming) If device transfer rates limit your operations and if the necessary network bandwidth is available, you may want to set up your operations to use all of the available devices at once. By distributing the data across parallel streams, this approach greatly reduces the time required for backup operations. It does, however, consume more network bandwidth. Recovery after a catastrophic loss may be faster, since all available devices collaborate to restore all or most of the backup data at once. CA ARCserve Backup has the capability to automatically create multiple streams based on the availability of tape devices. 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. Online Recovery Data Storage Requirements 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 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 26 Implementation Guide