Amazon EBS Snapshots Explained
Cloud-based storage is growing, allowing companies to scale their storage capacity regardless of their computing power. Backing up the data stored in the cloud is just as important as backing up your own computer. Amazon Web Services (AWS) offers a solution in the form of Elastic Block Store (EBS), which you can use to back up your -servers (EC2 instances).
EBS is a block storage solution, which organizes the stored data into bytes and arranges them into blocks, each of acting as a separate hard drive. In the world of AWS, blocks are referred to as EBS volumes.
To back up the data in your EBS volumes, Amazon has developed EBS snapshots. This disaster recovery solution works by copying your EBS volumes at specific points in time. Should disaster strike, you can restore your data from the latest snapshot.
In this post, I’ll examine how EBS snapshots work and discuss the major advantages and disadvantages of using this as your backup solution.
How Do AWS EBS Snapshots Work?
EBS snapshots work as an incremental storage system that captures and stores each moment-in-time snapshot of your EBS volume. All snapshots are stored in Amazon Simple Storage Service (S3). The next time a snapshot is taken, only data that was not included in the previous snapshot will be stored.
EBS snapshots can thus be used to track how your EBS volumes have changed over time, whether a new volume was created or an old volume modified.
For volumes that already existed in previous snapshots, a reference is made connecting the new snapshot to the first snapshot where this volume appeared. The snapshots are then chained together internally, creating a clear history of your data and allowing you to restore your data to any point in time when a snapshot was taken.
What if you delete an old snapshot, will this not have repercussions for all successive snapshots? The answer is no. If you delete an old snapshot, AWS will consolidate all your snapshots data. Only the data that is unique to that specific snapshot will be erased. The data which is not unique to the deleted snapshot will simply be moved to the next snapshot.
The Pros and Cons of Using EBS Snapshots
The main advantages of using AWS’ EBS snapshots are:
- Comprehensive backup — having a solid system for backing up your data is critical. EBS snapshots allow you to restore your data to any point in time when a snapshot was taken and enables you to delete old snapshots without worrying about data loss for valid data.
- Reliability of Amazon S3 — when you are backing up your data with a third party, you want to make sure you are in good hands. Amazon’s S3 is an industry-leading cloud storage service. The infrastructure is reliable and it is generally cost-effective.
- Time savings — because EBS snapshots are an incremental back-up system, backing up will be a fairly quick process. Once all your block-level data is saved to your S3, only changes on the block level will be recorded. This is much quicker than a full back-up.
- Cost-efficiency — storage costs money and costs can balloon as your company grows. The incremental nature of snapshots eliminates redundancy in your backups, which can help reduce your storage costs. Likewise, they take up much less storage space and are thus cheaper than the heavier EBS volumes they capture.
The main disadvantages of using EBS snapshots are:
- Longer recovery time — incremental storage solutions avoid duplicating data, and while this has many advantages, it also means that recovering your data can take longer. Because all the snapshots are linked together, the system needs to work backwards to the first snapshot in the event of recovery. The recovery time will thus be much slower than a full backup solution.
- Data cannot be copied outside AWS — when it comes to protecting yourself from total data loss, redundancy is key. Because your EBS snapshots are stored in S3 and you do not have direct access to your snapshots, you cannot back up this data outside of AWS. This could prove problematic should S3 suffer an outage.
- Potentially costly — snapshots take up substantial storage space, and you are paying for this. If you are simply accumulating snapshots without deleting ones that you no longer need, it can become a costly solution.
Should You Use EBS Snapshots?
Backing up your data is of critical importance to ensuring business continuity in the event of a disaster. Using a cloud-based backup system can help with the headache of buying and managing on-premise servers for storage. While EBS snapshots are not a perfect solution, they have many advantages.
First and foremost, just the fact that Amazon is standing behind it means a lot. It does not mean that crashes are impossible, but when it comes to infrastructure quality, Amazon is the gold standard.
Secondly, EBS snapshots provide an incremental backup of your data. This saves you time and money by avoiding redundancy. Moreover, in case you want to delete an old snapshot, AWS will consolidate all the valid data for you and make sure you do not lose any relevant information.
This is especially useful because you can save on storage costs by routinely cleaning up your snapshots and removing any that you no longer need. Should disaster strike, it may take longer for you to restore all your data, but this may well be a worthwhile alternative to spending the time and money needed to store a ton of redundant information.
