Automatic File Mirroring

Question

Is there any program where, if I have my computer connected to my external hard drive and download something to the computer's internal hard drive, it then mirrors this out to the external hard drive? I am looking for something as transparent as RAID.

• Ideally, this process would be entirely automated.
• Open source software and linux compatibility would be a plus.
• If it requires either a batch script or shell script I am perfectly fine with that.
• Synchronizes in real time or, if that's not possible, at least in intervals

The primary goal simply is to duplicate my data onto external media in real time at best and something like timed intervals at worse. Also, in backing data up I wouldn't want to use a script that just completely overwrites the mirror drive. I want it to realize where changes were made and as such change the mirrored system to reflect these changes.

Answer 1

Second Copy from Centered Systems will do exactly what you want.

It will create a mirror copy of any data you specify. It is very flexible.

It can be obtained from www.secondcopy.com

Good luck!

Answer 2

git-annex might be a good candidate here. You can think of it as a kind of "open-source Dropbox and more". It can work locally, via network, with online media.

At a first look it might seem a bit "confusing and hard to set up" – but luckily there's git-annex assistant which makes things easy (just look for that at Youtube for some nice presentations). For your case, I'd recommend using that to set up two "annexes": One is the download directory on your local harddisk, and the other is your "external drive". Now, everything you drop in one place, is easily "known" on the other – though by default not "physically there". For the latter, you simply declare the entire "local harddisk annex" as "preferred content" in your "external annex" – which then would take care to automatically make the content itself available there (instead of just the metadata).

^{git-annex assistant guides you through the setup process in easy steps (click images for larger variants)}

The entire process is not usually triggered immediately, but might have a short delay (the daemon checks in intervals AFAIK). git-annex works fine on Linux and Android (not sure about other systems, but if I remember correctly, also on Mac and Windows).

^{a git-annex assistant demo screen: matches your situation with the USB stick :)}

Some additional links which might prove useful:

• How can I install git-annex assistant (on our sister-site AskUbuntu)
• file manager integration
• git-annex projects at Github (addons, plugins, manuals, you-name-it)
• Managing a large number of files archived on many pieces of read-only medium (E.G. DVDs)
• Managing Backups With Git-annex
• backends and special remotes (your external harddrive might fall into the latter category)

Answer 3

You don't mention that it must be free. I would highly recommend paying US $19.99 for a personal version of Bvckup 2. I did, and I have never regretted it.

I did a lot of research before choosing it, and what convinced me was partly that it supports VSS, so that it can synch files which are in use, and, especially, the speed, it wins every test because it uses delta copying:

Reduce the amount of data being moved around by copying modified parts of files only. This speeds things up, in many cases dramatically.

.

There is a 5 start review of it at PC World.

If you don't want to spend, or just want to try it out, the last beta, which is quite recent, is available here.

If you still don't like Bvckup2, then I can highly recommend FreeFileSynch, which I previously used. See my long answers to this SR question, and this one and this one too.

To save you the trouble of clicking those links, here is the feature list:

Key Features

Detect moved and renamed files and folders
Copy locked files (Volume Shadow Copy Service)
Detect conflicts and propagate deletions
Binary file comparison
Configure handling of Symbolic Links
Automate sync as a batch job
Process multiple folder pairs
Comprehensive and detailed error reporting
Copy NTFS extended attributes (compressed, encrypted, sparse)
Copy NTFS security permissions
Support long file paths with more than 260 characters
Fail-safe file copy
Cross-platform: Windows, Linux, Mac OS X
Expand environment variables like %USERPROFILE%
Access variable drive letters by volume name (USB sticks)
Native 64-bit support
Keep versions of deleted/updated files
Prevent disc space bottlenecks via optimal sync sequence
Full Unicode support
Highly optimized runtime performance
Include/exclude files via filter
FreeFileSync portable and local installation available
Handle daylight saving time changes on FAT/FAT32
Use macros %time%, %date%, et al. for recurring backups
Case-sensitive synchronization
Built-in locking: serialize multiple jobs running against the same network share 

Supported Operating Systems

Microsoft Windows Microsoft Windows FreeFileSync runs natively on all 32 and 64-bit Windows versions:

Windows 10
Windows 8.1
Windows 8
Windows 7
Windows Vista
Windows XP
Windows 2000