In May 2017, a massive cyber-attack caused by WannaCry ransomware. Such attack has increased the awareness of the importance of backups. However, many system administrator, especially novice ones faced the consequences of improper backup strategies that are never tested. Such strategies mostly lead into a huge chunk of missing or useless data. Fortunately, there are a set of recommended tested strategies that insure no data loss as much as possible. One of these strategies is what is known as 3-2-1 Strategy Back up.
The number three means that each file must be three copies of each file. Moreover, it also means that all files are identical and have exact check sum value. Check summing is a calculation done using certain algorithms, that ensures integrity of data were not changed after sending them into a medium.
Three copies are recommended instead of three, because in some scenarios even the backup files might fail. An example of such scenarios is when a system is hit with a malware that encrypt all files attached. Different media is recommended because each medium has a different
Second, number 2 means these copies are save in at least two different back up media. These media could be a conventional hard disk drive, a tape, or even an optical disk such as DVD or Blu-ray. Moreover, cloud storage can be considered as a media, even though it uses one of the previously mentioned media.
Last, number 1 means that at least one copy must be offsite. It is advised that the offsite location is at least 25 KM away from the original copy. Offsite copies are critical when original location was affected by a catastrophic incident such as a flood, fire and earth quakes. Moreover, physical security should be implemented and assured when offsite location is run and manage by corporate itself.
No matter how many copies do you have of a file if these copies are not identical and corrupted. Thus, after ensuring that files are copied as mentioned above, ensure that are the identical and retrievable every six months. You really do not want to get back to a backup and nothing is there.