Backups Aren't Simple

Backups may seem straightforward, but they're not as simple as they appear. A comment once highlighted that there are two types of people — those who have experienced catastrophic data loss and those who will inevitably face it. This is true for most of us, as data loss is a common occurrence, often happening at the most inconvenient moments.

I can relate to this firsthand; when I was younger, we moved our family photos from our computers to an external hard drive to save space. This was a success until my dad decided to use the drive for his TV set-top box and accidentally formatted it. The files were lost, and we were left with an empty drive. This incident taught me the importance of backups, but also the challenges involved in managing them.

Data loss can come in many forms, from hardware failures to software errors or even malicious attacks like ransomware. It's crucial to have a backup plan in place, which involves creating copies of your files in a different location. However, simply having a backup isn't enough; we need to consider potential threats such as ransomware, human error, or system corruption. This means our backups should not be exact replicas of the original data, as we also want to be able to revert to previous versions if needed.

One approach is to take snapshots of your data, which allows you to restore previous versions if something goes wrong. The frequency of these snapshots depends on your Recovery Point Objective (RPO), which is the maximum amount of data you can afford to lose. For example, a financial institution might aim for a RPO of just 30 seconds, while a small enterprise might settle for 24 hours or more. Regardless of the RPO, you'll end up with a growing collection of snapshots, each taking up more storage space.

To manage this, you'll need to rotate your backups. This means deleting older snapshots to make room for new ones. The frequency of snapshots should increase as you move towards more recent data, with more frequent backups for recent files and less frequent ones for older ones. This approach can help balance storage usage and data recovery capabilities.

Another strategy is to use deduplication, which involves storing only the changes between snapshots instead of full copies of files. This can significantly reduce storage requirements, as it takes advantage of the fact that many files remain unchanged over time. Tools like rsnapshot utilize this technique, storing only the differences between snapshots and referencing existing files to save space.

In summary, while backups are essential, they require careful planning and management to ensure they serve their purpose effectively. By understanding the potential risks, setting appropriate RPOs, and implementing strategies like snapshotting and deduplication, you can create a robust backup system that safeguards your valuable data.