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Volume Clones

2018-05-11 23:22:58 Chip Page 1019 📢 PUBLIC

A clone begins as an exact copy of the original disk. One of the clones is left untouched while the other is used and updated. The clones have internal data structures that let CryptDisk quickly identify differences that accumulate over time. CryptDisk can then restore the clones to being exact disk images by copying only the portions of the disk that have changed. This is much faster than copying the entire disk.

Cloning a volume serves two purposes, archive and transfer.

Archive

The clone is created as a backup of the original volume and is only used in case of a data disaster. The original volume continues to be used and updated. The clone is used to restore the disk to the exact state when the backup was created.

Transfer

Let's say I use two different computers, one at home and the other at work. I want to access my personal information (email, documents, etc) from both computers without using untrusted "cloud" servers. I create a CryptDisk volume to hold all my information.

The original volume is created on my home computer as C:\Users\Me\Documents\MyData.dsk. Now I want to take this disk with me to the office, so I create a Clone on a thumb drive as M:\MyClone.dsk. I don't want this to be the official disk because the thumb drive is slower than the internal drives and easy to lose, the thumb drive is just a temporary location while I am in transit from one compuer to the other. At the office I use CryptDisk to clone M:\MyClone.dsk to the office computer as C:\Users\Me\Documents\MyData.dsk. I then mount the local volume and use it. At the end of the day, I unmount the volume and clone it back into the existing M:\MyClone.dsk on the thumb drive. CryptDisk is able to copy only the sectors that have changed, resulting is a very fast differential update. At home, I clone M:\MyClone.dsk back into C:\Users\Me\Documents\MyData.dsk. This is another fast differential update.

Fast differential copies are crucial to making this a convenient process, since it involves copying the volume four times each day. CryptDisk makes this even more convenient by providing a macro operation to automatically clone a set of volumes with a single click.

Clones are copies of a volume that can be used for differential updates and restores. It is important to understand that cloning is an optimized disk copy resulting in an exact copy of the source volume. It does not merge differences, any changes on the destination volume will be overwritten and lost.

There can be many copies and versions of a volume, but only one is the active volume. Only the active volume can be updated, any updates to other versions will result in a data fork that cannot be resolved.

CryptDisk prevents data forks by selectively locking and unlocking volumes, and only allow updates that will not create a new fork.

Locked volumes can be mounted for Read-Only access but cannot be updated or modified.


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