Real world encrypted container (TrueCrypt)

zpaqfranz is excellent for making backups of encrypted or unencrypted volumes, such as TrueCrypt/VeraCrypt, Microsoft VHD/VHDx, virtual vmdk/vbox

To be sure of making a reliable backup of some data, it is possible to adopt a particular but effective strategy (we will refer to Windows but it is the same for other systems)

Suppose we have a certain amount of data that must be safeguarded to the maximum extent, in every single bit. Using archiver such as 7z, rar, rsync, robocopy or the same zpaqfranz, operating on a filesystem to backup the (say) e:\data folder, the problem remains of not having an image of the data, but a backup. You can use software such as Acronis etc to create an image backup (sector or cluster level), but generally the space occupied is very large, even using differential, incremental, etc. methods

Let now consider storing our data inside a TrueCrypt/VeraCrypt/VHD/VHDx (...) container file, which will be mounted at boot. We will therefore have a giant file (for example) e:\parte\myvolume that we will mount as (example) drive f:\ on Windows

Using TrueCrypt/VeraCrypt also has the side effect of encrypting data, which is good and fair

Our problem then turns from copying the contents of the Windows f:\ drive to making a copy of the container file e:\parte\myvolume, once dismounted

This is essentially impossible with ordinary methods as the size of the created file will be the same as the original one. If the volume is large for example 30GB, the 7z copy (or rar or tar) will be exactly 30GB, it is not possible to compress an encrypted volume

The same for zpaqfranz: the FIRST backup will be 30GB

However, what normally happens is that multiple data backups, for example daily, are taken.

Every day, using 7z (/robocopy...) for example, I will use 30GB of space, because the whole volume will be copied

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But with zpaqfranz ONLY the differences will be added, maintaining the "from always to always" image-level backup. How?

zpaqfranz a k:\test\cloud\provona.zpaq e:\parte\myvolume -force -method 0 -checksum -pakka -test

k:\test\cloud\provona.zpaq  = the output file
e:\parte\myvolume = the giant unmounted file
-force = do not care of timestamp (TrueCrypt does not change)
-method 0 = do not compress (only deduplicate). You can't compress encrypted data
-pakka = smart ETA (or use -noeta for batch)
-test = verify just after add

Now you will get a k:\test\cloud\provona.zpaq backup of the e:\parte\myvolume, 30GB (in our example). The next day we will mount the volume as f:\ write something (ex. 100MB) etc, unmount Then, again

zpaqfranz a k:\test\cloud\provona.zpaq e:\parte\myvolume -force -method 0 -checksum -pakka -test

What will happen? The k:\test\cloud\provona.zpaq file will grow for (say) 100MB, becoming 30.1GB, and again for the next days (30.2GB, 30.3GB... 31GB... 32GB... 40... 50GB)

Conventional archivers require 30GB x day growing very quickly to unfeasible size. zpaqfranz, instead, after the first "big" run will consume as little as possible space, maintaining all the data

For uncrypted volumes you will NOT use -m0 (therefore maintaining compression as default)