The simple value of archiving…

I am flying from the east coast to the west coast to close out the “Evolution of Disaster Recovery” seminar series, with show 7,8 and 9 in LA, Orange County and San Diego respectively. As part of the seminar I spent a significant amount of time discussing Backup, Recovery and Archiving (BURA). I thought it might be a worthwhile endeavor to document this a little further and seeing that I have 6 hours to kill there is no time like the present.

The following example assumes a 5 week backup rotation, which is fairly common. In the event that you have a backup rotation that archives monthly backups for one year and yearly backups for 7 years, etc… the model grows exponentially. Typically most backup policies consist of incremental backups which are taken Monday through Thursday with a weekly full backup on Fridays. Tape sets are vaulted for 4 weeks, on week six week fives tapes are recycled, this rotation maintains 4 offsite copies at any point in time. Assuming a typical weekly rate of change of 10% data duplication is massive which extends backup times and raises cost due to the amount of media required. The following is a graphical representation of a typical 5 week rotation:

typical 5 week backup rotation

By introducing an archiving strategy we can greatly reduce the amount of data that is duplicated in the offsite facility and remove stale or unwanted data from the production data set which greatly improves backup and recovery times. The archive is an active archive which means that archived data is replaced by a stub (not a shortcut, stubs are not traversed during backups) and moved to an archiving platform of choice such as ATA(Advanced Technology Attachment), NAS (Network Attach Storage), CAS (Content Addressable Storage) , tape, optical, etc… – The user experience is seamless. A sample of what an archiving strategy might look like is represented by the following graphic:

typical 5 week backup rotation archiving

Some duplication will continue to exist due to the fact that we may have frequently accessed data that we choose not to archive. The archive is static, any data that is read or modified is pulled back into the production data set thus there is no need to backup the archive on a daily of weekly basis. We refresh the archive backup following an archiving process which in this example takes place monthly.


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