Computer Associates BABNWUP900NE6 Administration Guide - Page 47

Defining Data-transfer Requirements Segmenting Your Network In many cases, you can make better use of your existing network bandwidth by placing BrightStor ARCserve Backup servers on different subnets. In the absence of subnets, all backup data has to cross a single network to reach the BrightStor ARCserve Backup servers. In effect, every piece of data travels sequentially to every node on the network. When you subnet your network, in effect you create two or more networks of equal speed, each of which handles a fraction of the backup data. Data travels in parallel. In our example, if we backed up 500 GB on two subnets instead of 1 Terabyte on the entire network, we could back up twice as fast. Each subnet could transfer its 500 GB at 36 GB per hour for a total elapsed time of 14 hours (versus 28 hours). In our 5-hour backup window, we could transfer 360 GB, which, though not enough, is still far better than the 180 GB we could attain over a network that is not subnetted. Segmenting Your Data Nothing forces you to treat all of your organization's data as a single unit. It often makes better sense to segment the data into logically related chunks before trying to back it up. This reduces the time required for any single storage operation, makes better use of short backup periods and works better on slow networks. You still back up all of your data. You just do it in a series of shorter operations spread over several days. We might, for instance, back up 20% of the 1 Terabyte of data in our example each night, Monday through Saturday. In the course of a week, this approach would back up our entire 1 Terabyte across the 100Base-T network, without exceeding the daily 5-hour backup period. As an added benefit, the compact backup elements make locating and restoring our data faster and easier by reducing the scope of searches. The downside of this approach is that the entire data will not be backed up daily. Most organizations cannot afford to not have daily backups of complete data; therefore, this approach may not be suitable. Planning 2-9