True Image Verify Question

[howie123]

Hi, guys...
I was just curious if the verify function in TI (I'm using TI 10) actually does a bit by bit verification of the original data or uses some other method to determine the validity of an image.
Thanks for any responses!
howie

[vukodlak75]

Intersting to know

[MudCrab]

As posted by seekforever:

The validation process causes the archive file to be opened, read and the checksums to be recalculated and compared with the ones stored in the archive file. There are 4000 checksums per gigabyte of archive and they all must agree perfectly or the archive is declared corrupt.

TI does not do a bit-by-bit validation. There is no comparison between the original data backed up and the data stored in the image file.

[shieber]

Note that this method of validation can give a false negative. Basically, a crrupt file declaratiin rally means, unable to successfully recreate the same checksums. This could be becasue a file is corrupt. However, if the program cannot proporerly read the file, it will not be able to successfully match checksums even though the file might fine. Some folks experience this when trying to validate a file on USB that validates fine on an interanl drive -- or when using the bootCD. However, as often noted, if the prog can't validate a file when run from the bootCd, there's a good chance it woun't be able to read the file properly to do restore, even thought the file is fine.


So, at best, it's an ersatz method for verifying a file's integrity and fidelity to the original data. Why do it this way? Usually, the original data no longer exists (not all of it) -- system drives keep changing all the time, same with data files, sometimes even while the backup is being created. So a methof to compare to the original data is problematic in at least a couple of critical ways.

[howie123]

Thanks for the replies, guys... Someone in another forum had asked about verify times and another poster explained to me that a created image cannot possibly be compared to the data originally backed up as this is always changing, even immediately after or during an image (if imaging is done inside the OS). I appreciate the info! :-)