One job the archive must do is to provide a mechanism by which all the images can be verified and validated. This is a key functions ImgArchive provides ensuring that all images are free from corruption or damage.
If corruption is found then other mechanisms are included in ImgArchive to copy affected images from a backup thus repair the damage.
Validating Repositories
All the repositories in the archive can be validated at anytime. This includes both Vault and User repositories.
These are selected using the scope argument, by selecting a scope. The scope values are as follows:
Validated Vault Repositories
The Vault Repositories consist of the Master and Derivative repositories and there two backups.
The scope of Master, Derivative and Vault selects the main repositories. This selects the main repository.
Using the —scope argument by default includes the main.
By adding the —validate-backups selects optional backups.
If on the other hand the main repository is not to be included the option —no-main
This mechanism consists of finger printing each image then comparing the finger prints at a later date to the images to verify that the image has changed. If this is the case then the image is damaged. To repair the damage a backup can be used to replace the corrupted image.
Check Disk Data file
This file contains the fingerprint for each image in the day folder. Each fingerprint contains the following:
Name of image file including the extension.
64bit CRC.
MD5.
Status.
Time created.
Time modified.
If checked out.
Size of file.
One problem with this is that the Check Disk Data file can itself be corrupted