EBS snapshots vs. WAL-E for PostgreSQL on EC2

Question

I'm getting ready to move our posgresql databases to EC2 but I'm a little unclear on the best backup and recovery strategy. The original plan was to build an EBS backed server, set up WAL-E to handle WAL archiving and base backups to S3. I would take snapshots of the final production server volume to be used if the instance crashed. I also see that many people perform frequent snapshots of the EBS for recovery purposes.

What is the recommended strategy? Is there a reason to archive with WAL and perform scheduled EBS snapshots?

Answer 1

The EBS Snapshots will give you a slightly different type of backup than then WAL-E backups. EBS backups the entire drives, which means if your EC2 Virt goes down you can just restart the virt with your last EBS snapshot and things will pickup right where you last snapshotted things.

The frequency of your EBS snapshots would define how good your database backups are.

The appealing thing about WAL-E is the "continuous archiving". If I needed every DB transaction backed up, then WAL-E seems the right choice. Manys apps I can envision cannot afford to lose transactions, so that seems a very prudent choice.

I think your plan to snapshot the production volumes as a baseline, then use WAL-E to continuously archive the database seems very reasonable. Personally I would likely add a periodic snapshot (once a day?) to that plan just to take a hard baseline and make your recovery process a bit easier.

The usual caveat of "Test your recovery plans!" applies here. You're mixing a number of technologies (EC2, EBS, Postgres, Snapshots, S3, WAL-E) so making sure you can actually recover - rather than just back - is of critical importance.

Answer 2

EBS snapshots will save the image of an entire disk, so you can back up all the disks in the server and recover it as a whole in case of data loss or disaster. Besides that, the block-level property of EBS snapshots allows instant recovery, you can have a 1TB database restored and have it up and running in a few minutes. To recover a 1TB database from scratch using a file based solution (like WAL-E) will require copying the data from S3 first, a process that will take hours. Using WAL files for recovery is a good approach, since you can go back to any time by transaction, but snapshotting the entire server will include WAL files as well, so you’ll still have that option. The backup and rapid recovery process using EBS snapshots can be automated with scripts or EC2 backup solutions (for example, Backup solutions for AWS EC2 instances).