So I was thinking of implementing the rsync / hardlink /snapshot backup strategy and was wondering how much data a hardlink took up, like it has to put an entry for the extra link as a directory entry etc. Anyway I couldn't seem to find any information on this and I guess it is file system dependent. The only info I could find was suggestions they took no space (probably meaning they take no space for file contents), to the space they take is negligible to they only take a few bytes to store the hardlink.

So I took a couple of systems (one a vm and one on real hardware) and did the following in the root directory as root:

mkdir link

cp -al usr link

The usr directory had about 54,000 files. The space used on the hd increased by about 34MB. So this works out around 600 bytes per hardlink, or am I doing something wrong?

Thanks very much.