Storage Basics: Backup Strategies
It is certainly not news to say that the amount of electronically stored data is growing. It's because of this increase in storage space requirements and the trend towards data centralization that our backup solutions must scale to SAN and NAS storage demands in terms of speeds, reliability, and security. Because of the importance backups play in the design and implementation of a storage strategy, they must be carefully considered.
As we know, a backup is simply a copy of electronic data which is used as a means of recovery should the data become lost, corrupted, or compromised. Though the definition of a backup may be straightforward, the actual implementation of a storage backup solution can be a difficult task that encompasses many obvious and not so obvious considerations.
In the next two storage basics articles, we'll explore some of the factors to consider when implementing a backup solution for a storage area network, starting with one consideration that dates back to the origin of the Local Area Network — dealing with the backup window.
Dealing with Shrinking Backup Windows
A backup window refers to the time it takes to complete a given backup. This backup window is determined by both the amount of data that must be backed up and by the speed of the network infrastructure that handles the data. For some organizations, the backup window doesn't present any real problems. Such organizations typically have the ability to complete data backups in the off hours without running into production time.
However, as the amount of data grows, so too does the time it takes to perform the backup, and soon backups will run into production time. Further, many organizations today do not have an off hours period — they require network access 24/7, leaving a very small or even nonexistent backup window.
There are many ways to address the backup window issue, and the one chosen will depend on the needs of the organization, budgets, and of course the amount of data that must be backed up. Some of the methods used for operating within a backup window include using differential and incremental backups, snapshots, hardware and infrastructure upgrades, and potentially modifying the network backup design using server-free and LAN-free backups.
Starting at the beginning, some of the oldest methods of dealing with the backup window are using incremental or differential backups instead of regularly performing full backups. Before designing a backup solution with these methods, it's important to first have a solid understanding of backups in general and what each of the alternatives is designed to do.
A full backup saves all directories and files, and while it might sound ideal to perform a full backup every time we back up our data, the backup window often prevents this. Because of the time and media space a full backup can take, they are often restricted to a weekly or monthly schedule, although the increasing speed and capacity of backup media is making nightly full backups a much more realistic proposition, even for those with hundreds of gigabytes of data.
Full backups, if you have the time to perform them, offer the ultimate in data protection. In effect, a single tape, or set of tapes, can provide the ability to completely resurrect a server to its current state. Full backups are not, however, without their drawbacks; one of which is security-related. Each tape contains an entire copy of the data on a given server. If the tape were to be stolen, the thief would then have an entire copy of the data.