Computer Associates BABNWUP900NE6 Administration Guide - Page 42

Defining Data-transfer Requirements Defining Data-transfer Requirements The overall data transfer rate for your backup and recovery system sets the amount of time required for storage operations. You have to balance your backup window, backup data, and recovery speed requirements against the capabilities of your existing infrastructure and the budgetary constraints of your organization. What is Your Basic Data-transfer Requirement? After you have quantified the amount of data that you have and the times when you can back it up, you can roughly estimate the minimum data transfer rate that you must achieve to fully back up the data in the allotted time. Use this requirement as a starting point for the decisions you make later in this chapter. To calculate a rough, minimum transfer rate, divide the amount of data by the amount of time available to back up the data: databackedup ÷ backup_window = required_rate For example, if you have 1 Terabyte to back up and 5 hours available each night and you intend to back up everything in one session, you need to achieve a rate of 200 GB per hour. What is the Data-transfer Rate of Your Backup Hardware? Your backup hardware is unlikely to be a limiting factor in reaching your target data transfer rate. Most devices are very fast. However, you should evaluate hardware speed at the planning stage. At a minimum, you must have enough hardware, or fast enough hardware, to write your data to storage media within the time allowed. Smaller numbers of fast devices or larger numbers of slower devices can often achieve the same total throughput. Use the information that follows to estimate the aggregate data transfer rate for your hardware. SCSI or Fibre Interfaces No device is faster than its connection to its data source. Current backup devices connect using standard SCSI or fibre interfaces. The following table lists the common varieties. Version Wide Ultra SCSI Ultra2 SCSI Bus Width Approximate Maximum Data-transfer Rate 16 bits 40 MB/seconds=144 GB/hour 8 bits 40 MB/seconds=144 GB/hour 2-4 Administrator Guide