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I have only one single file I want to backup. This file will either be in binary format or I can run a command line utility which converts it to a text file if it will help the backup solution. The file is about 500MB at the moment, but can easily grow to several gigabytes and even more.

I'm looking for a backup solution which will allow me to create several versions (e.g. daily, weekly, monthly) of this file but won't take up too much disk space.

For example, say I want a daily, weekly, and monthly backup. That's 3 files. Assuming the size stays fairly similar, this will take up 1.5GB of space. What I want is a very efficient algorithm (similar to SVN's diff) which only saves the differences. So for example, the monthly backup will be a full backup (500MB) and the weekly and daily will simply be diffs which will probably be even less than 2 MB each. Thus my 3 files will take up only 504MB instead of 1.5GB.

I know that many backup utilities have similar functionality, but they focus mainly on diffs of the files themselves (e.g. which files were added/removed) rather than focusing on diffs of the file's content (e.g. which lines/characters were added/removed). With only a single file to backup, it is obvious why one of those solutions wouldn't help.

Extra features which I would like, but aren't critical:

  • Built into Windows XP.
  • Encrypted backups is a plus.

Update: I tried Areca Backup and didn't get the results I want. This is the process I use:

  1. Create a large file (e.g. 600KB)
  2. Back it up
  3. Change a single letter in this file and save it
  4. Back up again
  5. Examine the size of the archive. If it is nearly double (e.g. 1.2 MB, the file was copied, and this is not the kind of backup I am looking for. If the size is very close to the original size, 601KB, for example, this backup was successful).

As you can see, it doesn't make sense to store 600KB again when only one char was modified, that's why I'm looking for a smarter backup solution.

I tried using the "Delta" storage mode and both the incremental and differential backup types in Areca, but they all failed my test.

I also tried DeltaCopy, which says:

In general terms, DeltaCopy is an open source, fast incremental backup program. Let's say you have to backup one file that is 500 MB every night. A normal file copy would copy the entire file even if a few bytes have changed. DeltaCopy, on the other hand, would only copy the part of file that has actually been modified. This reduces the data transfer to just a small fraction of 500 MB saving time and network bandwidth.

The problem with it is that it only uses this differences for the network transmission. It doesn't allow you to save multiple versions of files. It also relies heavily on client/server technology which I don't need. I just need something that works locally on my PC.

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2 Answers

Genie Backup Manager is what you're looking for. You can setup when to backup and encrypt the files. You can also setup whether to fully backup or only incremental. Maybe their Timeline does the job for you, too.

Another solution I get in mind is Dropbox. It's a free online storage service which has incremental uploads and got some version control.

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rdiff-backup, Comodo Backup, Duplicati, and CrashPlan will all give you what you want.

They all do much more than that, but give you the one feature you're looking for.

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