I am looking some software for backup to an external HDD that will essentially mirror my computers documents in their current state, i.e. if I delete or modify a file that modification is applied to the backup and the previous version is removed. It needs to do this live and automatically. Any suggestions?
I've been really happy with Allway Sync. It can do a unidirectional or bidirectional sync. It can be initiated on a timer, on an event (like plugging in the external drive), or simply always-on. It can keep records of your old files, or you can turn off that option.
It's free for personal use. Very nice program.
As per my answer here ...
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.
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
You might want to try autover, which is described by the author as,
real time backup and personal versioning system.
It let's you configure exactly this behavior, but if your requirements should change at some time, you'll be able to adapt quickly and easily.