Backups
From Sysadmin
Backups are maintained so that data can be recovered in the event of a disaster. Today, both home and corporate users rely heavily on their computers to store important data. Backups have become an essential component of modern computing for all users. High availability options such as multi-site replication are not a replacement for backups.
It is essential that backups are done as part of a Backup strategy.
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History
Backups have nothing to do with modern technology. Backups are a way of retaining data in the event of the loss of storage media. The data itself is independent of the storage media. The issue of backups have been relevant to humans for as long as there has been knowledge worth retaining.
Oral History
Passing information from person to person in a pre-literate society allowed for the propogation of knowledge but it also allowed for the information to be backed up. This is the only way that human knowledge survived from generation to generation for most of the time there have been humans.
Written Records
Monks in ancient Europe and Asia copied even more ancient texts by hand and distributed them geographically. In the event that a monastery was destroyed the surrounding monasteries would provide copies of texts in order to repopulate the library when the monastery was rebuilt. In doing so the monks were using an offsite backup strategy centuries before the term itself was coined. These monks copied their texts using a laborious manual process. In contrast making backups today is cheaper and faster. It is then a pity that so many modern organisations don't address backups adequately.
As a result of the hard work of these monks a large number of ancient texts survive to this day. We can now take over and use modern methods to preserve them for future generations.
Essential Criteria
It is impractical to try to predict all of the ways in which data could be lost and try to mitigate them. The only way to make sure that a backup allows for recovery of data following a disaster is to ensure that the backup conforms to several criteria.
The backup must be:
- Offsite
- Offline
- Tested
Offsite
An essential component of any serious backup strategy is that the backup be offsite. Only by keeping a backup offsite can the data be guaranteed to survive any single disaster. The only way to guarantee data survival following n disasters is to keep the data stored at n+1 seperate sites.
In particular RAID and Fire safes fail the offsite criteria and are thus not true backup strategies.
Offline
An essential criteria of any serious backup is that it be kept offline.
An online backup is subject to attack, such that the backup copies of the data could be erased along with the original.
An online backup is also subject to unintentional erasure or over-write. If an online backup is produced as a result of an automated sync process then the good backup could be over-written by the sync process following damage to the original data source. This may render recovery from this data source impossible.
Tested
A Disaster Recovery test is an important component of any backup and disaster recovery strategy.
Costs
Many smaller organisations balk at the cost of backing up and cut corners with their backup plan. They often don't have a disaster recovery plan at all.
A good backup strategy is quick and inexpensive to implement. A very good backup strategy tends to be more difficult to implement and very very expensive. As such it behooves organisations to implement a good strategy as quickly as possible, even if they subsequently improve it.
See Also
External Links
- The Tao of Backups - Has a commercial message at the end but the information presented is accurate and it is very well written
