Periodically someone will tell me that they don’t need to clone because they run cross-site backups. I.e., they’ll have an architecture such as the following:
Sample cross site backup configuration
Looking at a tape-only environment for simplicity, this configuration sees the backup media immediately off-sited by virtue of the tape library being physically located in another site.
The fallacious assumption made by some companies is that by running off-site backups, they don’t need to clone – their backups are off-site as soon as they’re generated, after all. This is incorrect, and can be readily shown when we evaluate a “site destroyed” scenario.
If the disaster recovery site is destroyed:
- All historical backup information has been lost. We have only the “current” data stored on site.
If the production site is destroyed:
- We are left with only one copy of our data, and can easily encounter a catastrophic single point of failure within the backup environment.
Therefore, regardless of whether you run cross-site backups, if you want full data protection, you still need to clone, so that:
- If the production site is destroyed, you don’t have to rely on single-copies of backups.
- If the disaster recovery site is destroyed, you still have access to historical backups.
Please, don’t make the mistake of thinking that cross-site backups are sufficient justification to avoid cloning.
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