How to execute & requirements

requires cygwin with perl "option"
run cygwin console with "right mouse click" -> "run as Administrator"
copy winpoolbackup to your cygwin-home-directory "cp /cygdrive/c/Users/xxx/Downloads/winpoolbackup.pl ."
create file backup-drive.txt on your backup drive (e.g. on the root directory of your drive -> "right mouse click" -> New -> Text file)
enter "perl winpoolbackup.pl" -- no commandline parameters required

Advantages

Every distinct file content is stored only once on backup drive
Filename nor PC nor drive nor directory does not matter, just the content.
Backups everything except system and programs; you do not have to think about which directories to backup.
Fast backup "algorithm".
You could keep the complete backup history without waste of backup space
Recovery is simple: every file is directly accessible on the backup drive
Encourages you to keep a lot of copies of all essential stuff on any pc drive, will not waste backup drive space any more.

for use with Windows only (adaption to *nix would not be a large effort)
X:\Windows and X:\Program Files* will not be backup'd. This is not a system backup tool.
NTFS formatted backup drive required
NTFS allows only 1023 links per file. This is not very much for content-identical files occuring often. So zero-sized files are not hard-linked, but created instead.
because using cygwin, no Windows/NTFS "attributes" are going to be transferred - like file permissions, ownership, encryption, compression. Just content and modification time. That's all.
be careful not to modify files on the backup drive, since every "copy" (there is no copy, just hard links) is being modified then.

Users of winpoolbackup.pl could enable (transparent) NTFS compression on the backup drive.

cleanup script for pool directory, removing any pool file not being linked from any HOSTNAME-YYYY-MM-DD--...-directory
does not build checksum during copying. Files could change during being copyied. But this is almost always problematic.
Escape filenames containing '\n'. Backup is not affected, just sha256.cache and poolfiles-firstname.txt
sha256.cache should not contain checksums from files that do not exist anymore (because filesize & memory).

Each HOSTNAME-YYYY-MM-DD--...-directory contains a backup-finished.txt - file to indicate sucessful completion
To get a chance to find out the original filename of any of the pool-files, there is a Y:\poolfiles-firstname.txt

Last edit: Jochen Barth 2014-07-13