Windows – Compressed, read-write file system within a single file

You can accomplish this using the 7zip command line tool and the windows task scheduler.

Download the 7zip command line tool from http://www.7-zip.org/download.html and extract it to c:\7zip

Open notepad and create a list of the directories you want to backup, one path per line

c:\users\username\important directory1
c:\users\username\important directory2

Go to tools->save and make sure to change the drop down menu from ANSI to UTF-8 and save the file as c:\users\username\backuplist.txt

Now, open the windows task scheduler and create a new task. Give the task a name and select to run it daily at your specified time. Select that you want to run a program and fill in the fields as follows

Program: c:\7zip\7za.exe
Arguments: a c:\backups\backupname.7z -r @c:\users\username\backuplist.txt
run in: c:\7zip

Now save the task and you should have a working backup solution based on 7zip.

I'm not sure which ones are available for Mac OS -- but there are still a lot of r/w compressed filesystems around:

• e2compr being a kernel-patch for EXT2
• Fuse offers a list of compressed filesystems, including such with r/w support like e.g. compFUSEd and LZOlayer_fs
• Solid File Sysem is multi-platform (explicitly states support for Mac OS X) and supports encryption as well as compression

So it is still possible, and is still done. Why it is not more widely known, I cannot tell...