Sep 092009
 

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

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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