3-2-1 backup rule for the cloud
When you perform backups, certain issues might occur. For example, you might find that you have backed up the wrong data or device, or that the backup failed or is corrupted. The classic 3-2-1 backup rule can help you improve your backups. The rule includes the following guidelines:
- Make three backups
- Two in different formats
- One offsite
For the cloud, offsite might mean keeping a tape copy in your local office, but this article also presents other options.
Make three backups
You should always make three copies of your backup. This guideline is based on Jack Schofield’s three laws of computing. The second law states that data doesn’t really exist unless you have at least two copies of it. As a result, best practices dictate that you need at least two backups in some form.
You can use Rackspace Cloud Backup for one of your backups. Cloud Backup takes a file-by-file backup on a schedule that you choose.
You might consider using a server snapshot for another backup. Server snapshots work for some servers in the Rackspace cloud. However, you should not consider them a backup solution. For example, if you are running a compute instance, your server is booting from a Cloud Block Storage volume. Server snapshots do not capture Cloud Block Storage volumes because they are performed on the host machine. With performance instances on which server snapshots do work, corruption might still occur if the snapshot is taken while a database table is being written to.
Two in different formats
We recommend that you make backups in smaller chunks that you can easily back up with Cloud Backup and sync to another location.
For example, you might first save your database backup locally, then compress your site files into a .zip file or .tar file and save them in a folder as well.
Then, make a backup that you save in another location.
You can create another job that runs at a certain time and sends those files to a third location. For example, you could have it copied to another server every four hours.
By using these methods, you back up your site files as a whole, and also create a copy in a compressed archived format that you save elsewhere in two different formats.
The offsite copy should be a local copy in your office. It should be available to your team if they need to access it to build a new server. For example, you might use an internal server to pull the files down, or have a server that is located in a separate data center from where your primary sources are located back up the files.
This section discusses the limitations that are associated with these backup methods.
Replication is useful in a multitiered cloud because if a server fails, a replica server keeps your site up and running. However, if you upload a corrupted file, the sync mechanism replicates the corrupt data. This corruption is a problem if you need to restore a server to a previous version.
You can use replication based on a scheduled task or a cron job. However, you might still want to be able to look at your backups within a certain number of days to see when things went wrong.
With Cloud Block Storage snapshots, there is no way to schedule a new snapshot and then delete the older ones. Snapshots also have the same corruption issues that server snapshots have.
Creating a total of three backups, two in different formats and one locally, is a tried-and-true practice for keeping your data safe. Remember to test the backups. Also keep in mind that your backup solution must adapt and change with new environments.
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