Disk-Based Backup With NAS Or VTL — Understanding Your Requirements By Dave Therrien, ExaGrid Systems

When considering a disk-based backup system, there are many branches in the decision tree to take into account when selecting the right solution for a given environment. Organizations with data from 1TB to 100TB in Ethernet environments tend to set up disk-based backup as a NAS target. Companies with data over 100TB, in a Fibre Channel environment, tend to set up diskbased backup with a VTL interface fronting the disk. To understand why this is the case, it's important to keep the following factors in mind:

Onsite Disk-based Backup – Short Term Retention

The first decision is how much retention you will put on disk at the primary backup location. If you plan to keep a week or two of retention onsite, on disk, then any standard disk will work. If you plan to keep four or more weeks of retention onsite, on disk, then the cost of standard disk will be prohibitive, and you should consider a disk-based backup system with built-in data deduplication technologies. For example, to keep 10 weeks of a 1TB full backup on disk, you will need 10TB of capacity for the full back-ups, plus additional capacity for overhead, RAID and your daily incremental back-ups. This can add up to a total requirement of 15TB in standard disk capacity. Without data de-duplication, this would obviously be too costly.

Dave has over 24 years of experience in high technology and data storage. Prior to ExaGrid Systems, Dave was the VP of Software Development at Storage Networks. Prior to Storage Networks, Dave was with HighGround Systems where he contributed to the success of its Storage Resource Management product. In 1987, Dave was a principal at Epoch Systems Inc, which was acquired by EMC in 1993. While at Epoch Systems, he designed a sophisticated UNIX-based backup and hierarchical storage management product. Dave has written numerous articles on storage networks and has done extensive research in new storage architectures. Dave received his BSEE from Northeastern University.