Understanding the Difference between Backups and Snapshots on Alibaba Cloud

Backups

A conventional backup comprises a copy of one or more files. Those files might be users’ documents on a file server, HTML or PHP files on a web server, email messages on a mail server, and so on. To create file-level backups on an ECS server from Alibaba Cloud, you can use the Hybrid Backup Recovery application (HBR) that is available from the management console and lets you create a cloud-based vault in which to safely create and store a backup until it is required. For added security and resilience, this can back up to multiple Alibaba Cloud geographic regions. Everything happens very quickly, because backups take place across Alibaba Cloud’s own internal network.

Snapshots

A snapshot is a complete copy of a server or disk at a particular point in time. You don’t get to choose which files get copied because the snapshot includes every file, the contents of RAM, any background services that were running, and the entire state of the server. Restoring a snapshot will revert the server to precisely the state it was in when the snapshot was taken.

Snapshot Suitability

It may at first seem that snapshots are similar to backups, but they are designed to serve very different purposes and should not generally be used in place of backups.

Snapshotting Running Instances

You can take a snapshot of an ECS instance at any time, regardless of whether the server instance is running or stopped. However, a running instance may be performing many background tasks, including complex database transactions. Or it may be part of a server farm, sharing its duties with other closely-coupled machines in order to provide fault tolerance or increased processing capacity. Therefore, snapshotting a running instance may require some careful consideration in order that you can be confident that the server can be successfully rolled back if required, without affecting other parts of the system as a whole.

Keeping Costs Down

To keep costs down, delete backups and snapshots that are no longer required in order to avoid unexpected monthly storage charges. HBR allows you to specify the retention period of the backup, with the default being around 2 years (730 days to be precise). You can change this to your liking. However, avoid making this period too short, or keeping too few generations of backup available, in order to maximise your ability to restore to a specific point in time. You can also delete backups manually on demand whenever you wish.

In Summary

Backing up your cloud servers is vitally important, and Alibaba Cloud makes this easy. To back up one or more files or folders, use HBR. You can also create snapshots, but these should not be regarded as conventional backups except in specific circumstances.

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