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Backup Solution: Three Methods
If you at least once archived the data (for example a family photo archive) you know: a full copy of the archive takes a long time and the archive itself a lot of space. Backup on a company scale exacerbates the problem because it is necessary to operate with large volumes of information. Three approaches to creating backups, which will be discussed below, and appeared as an attempt to optimize the backup process.
Full backup — no, there will not be a surprise — the information that was copied as a whole. A full backup is dual: it takes a lot of time to create (remember your photo archive) and it takes a little time to restore data from such a copy. The size of the full backup is as high as possible. The full backup method works well in that cases where the original data changes seldom and in a small relatively large copy volume.
The same photo archive structured over the years is a good reason to use a full backup: new photos for the year 2016 are unlikely to appear regularly and in large numbers.
Differential backup method
The essence of this approach is to move away from manipulating all information and copy only the changes relative to a full backup. The method compares the information from the full backup to the one that will be copied and then captures all the changes in the same copy. This process takes less time compared to creating a full backup, and the copy size is small.
To restore a differential copy, a full backup copy is requested and then a differential copy is superimposed on it. The time to restore a differential backup will naturally be greater than to restore a full backup.
For a family photo archive a complete copy of which consists of works of 2016 it will be useful to use a differential copy of those photos that you clicked in 2017. Intuitively this is often what they do manually adding to the archive folder 2017 fresh materials: winter-17, musical performance-17.
This method is optimal for those problems in which data changes seldom and in a small amount. Incremental copying works with changes relative to the last backup. In this case, for example, a combination of a full copy and several differential ones may appear as the «last backup».
Time to create an incremental copy will be even less than for a differential copy, and the copy size will be scanty. In addition this method is good for those tasks that need data recovery at different points in time: the helpdesk report at the time of Tuesday, the morning or the folder with the site layout for the new customer at the time Thursday. But it takes much more time to restore such a copy than in the case of the differential method: the folder and the report will have to wait a long time.
Let's return to the example with a backup copy of the photo archive, made up of a full copy of the photos for the 2016th and a differential copy of the photos of 2017. For flexible work with a backup of new, ever-changing photos —then you prepare materials for publication on your son's school website, then retouch landscapes to print and hang in the frame on the wall — it will correctly use incremental copies that, without damage to the archive, will roll back to «after the site, but before the landscapes».
You probably already felt: the organization of backup is a compromise. So it is: a compromise between the speed of information recovery and the duration of the backup process, between the amount of copied information and the type of backup procedure, between copying to a USB flash drive and a professional approach to the backup task.