[fh973]

Backups protect against bugs and operator errors and belong on a separate storage stack to avoid all correlation, ideally on a separate system (software bugs) with different hardware (firmware and hardware bugs), in a different location.

[chousuke]

The purpose of a backup is to avoid data loss in scenarios included in your risk analysis. For example, your storage system could corrupt data, or an engineer could forget a WHERE clause in a delete, or a large falling object hits your data center.

Snapshots will help you against human error, so they are one kind of backup (and often very useful), but if you do not at least replicate those snapshots somewhere else, you are still vulnerable to data corruption bugs or hardware failures in the original system. Design your backup strategy to meet your requirements for risk mitigation.

[gregmac]

I'd also add not just different location but different account.

If your cloud account, datacenter/Colo or office is terminated, hacked, burned down, or swallowed by a sink hole.. You don't want your backups going with it.

Cloud especially: even if you're on aws and have your backups on Glacier+s3 with replication to 7 datacenters in 3 continents... If your account goes away, so do your backups (or at least your access to them).