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Saturday, November 29, 2008

Backup Principles

The Principles of Backup
Years ago I ran into the The TAO of Backup  and loved it. Time has passed, and I still love its wisdom, even if I do tend to phrase things a little different, and is a great illustrated explanation backup principles:

  • Plan the Coverage, Frequency  and the Time Scope:backup every file in your care, do it in a frequency that matches the rate of produced work and its value, and be sure to maintain an 'archive window' of old backups, in a systematic manner, that will enable access to the oldest restore points you might need. 
  • Separation: Don't keep your backups near the source. With modern networks it is much easier than it used to be, and yet, when cold backups  are discussed, this wisdom is less remembered: make sure to keep the cold backups in a different space than that of the backed-up system. If possible, make sure that a copy of the cold backups is taken away from the facility to another place, bearing in mind major catastrophes. For family data, I would say such a ritual should take place on a yearly basis. For a large organization, even one with replicated data over several sites this may seem like something archaic, and yet I would recommend at least a 3 months cold copy archive (monthly basis would make me happier, but cost/benefit is a bitch). If you need to argue, remind your superiors that large organizations keep facilities in large cities, where large disasters may take place. Wouldn't it be safe to have one copy of the backup sent somewhere far and less central, for those rare disasters that terrorists might bring upon our heads? 
  • Security: Remember that backups must be guarded just as well as the original information. 
  • Testing and Integrity: Make sure that your backups are ok: that the medium is working; that the contents are the ones that should have been there; that they actually work in different test scenarios, from the nice to the least nice. When you plan test scenarios, harass different users from different departments; Imagine the stupidest accidents; Plan for the most horrible thing that can happen. Don't think I am paranoid. Instead remember: It is the role of the system administrator to take care. No one else is thinking of these situations. That is why you should. 

The summary of scope to planning backups
When approaching a backup plan the following should be taken into consideration: - Stability - Availability - time to restore - alternatives in disaster - another computer (cold/warm fail-over) - another site - backup quality - loss of information in restore (backup update frequency) - restore possibilities - ability to live with backup - Minimal Disturbance to Everyday Work during backup.

Useful links: 

What happens if you do not follow the advice brought here? Start practicing on the following song.

Yesterday: A DBA's Backup Song
(to be sung to the tune of Yesterday. 
 quoted from a copy of the Oracle Week Times - a leaflet
 given in Oracle Week 2000; Rob Cosgrove says he is the author.)

Yesterday, 
All those backups seemed a waste of pay 
Now my database has gone away 
Oh I believe 
in yesterday. 

Suddenly,
There's not half the files there used to be
And there's a deadline hanging over me 
The system crashed 
so suddenly.

I pushed something wrong 
What it was. I could not say 
Now my data's gone 
and I long for yesterday-ay-ay-ay.

Yesterday,
The need for back-ups seemed so far away
Thought all my data was here to stay 
Now I believe in yesterday. 


[update:  12/03/2010]