Preparations
- Use 3 hard disks: 1 original and 2 backups. Use the smallest disk as original.
- Keep all data that needs to be backed up on the "original" disk, which is permanently connected.
- Only connect the backup disks to the system to make backups.
- Encrypt both backup disks using TrueCrypt. This makes it possible to store them off-site.
- Always keep one of both backup disks off-site. Make sure you never have both disks in the same building at the same time.
- Make a backup every once in a while, for example each 2 months.
Backup steps
- Check the MD5 checksums of both the original and the backup disk (using ExactFile). This detects medium degeneration.
- Use a backup tool to copy the files from the original to the backup disk (using Second Copy). Make sure old versions of changed files are kept for a while.
- Eliminate duplicates of big files between the backed up latest version and the older versions (using Duplicate Cleaner). Only delete from the older versions directory.
- Create MD5 checksums for both the original and the backup disk. Store the checksum file on the disk they describe. Only include the newest versions of the files.
- Compare the newly generated checksum files between the original and the backup (using Beyond Compare). This ensures the backup was made correctly.
- Take the fresh backup off-site and bring the other backup disk back home. This way, there is a new version on-site (on the original disk) and one off-site.
Evaluation
- 500GB should be sufficient to store all valuable data. Only movies can fill this amount of disk space.
- As all data is stored on a single disk, there is no need for maintaining an index of what is stored where. The directory structure serves as documentation.
- The backup process requires only little effort, and it can be run at night.
- If one of the disks crashes, there are still 2 other copies.
- If one of the disks slowly degenerates, some MD5 checksums failures will occur. Then it is time to replace the disk.
- If a big file has small errors on all 3 copies, it might still be possible to reconstruct the original file (unless the errors are at the same location).
- In case of location dependent storage medium loss (fire, theft, electrical surge, ...), there is always a copy on the other location.
- In case of softwarematic modification and deletion (computer virus, ...), the file can be recovered from the backup disks. Because the disks are disconnected, the virus can not mess up the backups.
- Bugs or malconfiguration of backup software will be detected when comparing the MD5 checksum files.
- Because previous versions of the files are stored, deleted files can still be recovered, even if the deletion went unnoticed for a long time.
- Because the backup disks are encrypted, they can be safely stored at the office.
- When the password of the backup disks is forgotten, there is always the original copy. However, this situation should be avoided.
- The disk to be used for the next backup is always at home, so it is possible to immediately start making the backup when it springs to mind. The freshly made backup disk needs to be taken off-site only afterwards, so it requires no planning.
