Snapshots are not backups

DBA Experts

Snapshots are not Backups

by Yehuda Lasri


Snapshot Computer Storage

Although many people use them as backups and believe they are good backups. Snapshots are snapshots. Only backups are backups.

All components of a virtual server are represented as a file.
There was only one snapshot in a database server consisting of many databases with many mdf, ndf and ldf files.

A snapshot does not promise consistency locally or remotely.
There are systems that enable backuping up to every two seconds but our experience taught us that many companies work hard to find the 2 seconds in which the data and log files are consistent with the LSN as an inconsistency would not allow a good recovery of the backed up database.

A snapshot concludes of a momentary status of your database, therefore in case of an error when the snapshot was taken, a bad page or full transaction logs due to a long transaction the server might not start or get online for a long time and the snapshot would be useless.

A snapshot is made of a full image and a differential. If the image is corrupt or deleted your backup is useless.
When the base snapshot (weekly in this example) is corrupt you may not know and when that happened in a company despite having good bi-hourly differentials nothing helped and the company had to restore a more than a week old backup.

As long as a snapshot is not uploaded to a cloud it is useless because if the server gets corrupt its snapshot (on the same server) will too.

A snapshot can get halted and halt slow systems or make them unresponsive.

Database backups are still crucial and log backups are also necessary in order to get to 15 minutes or more back in time, for shorter times Always-On or Mirroring would be necessary.

Monitoring the well being and functionality of Replications, Always-On, Mirrors, Snapshots and Database Backups is thorough and built-in in Aimbetter.

Using snapshots as backups or failing to test backups randomly causes companies to lose money due to losses of data, long downtimes, loss of customers and employee hours and costs of consultants of malfunctioning backup software that can’t be monitored well and it all can be avoided by using snapshots properly and monitoring backups using reliable tools.

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