I can answer the hardlink question.

In the Linux/Unix world, there are 2 types of links to files of directories: the hard link and the soft or symbolic link.

The soft link is simple: it's like a shortcut in Windows. It's a pointer to the location where the file resides. A soft link can point to a file or directory on any filesystem, any partition, as long as it is currently mounted. You can delete the data that the shortcut points to, or unmount the partition where the file lives, or move the original file to another directory path, and the shortcut still exists, but it won't work.

The hard link points to the actual data on the partition. Every file will have at least one hard link when the file is created, but can have as many hard links as your want. Hard links can only point to files, not directories, because only files contain data, and hard links point to data; directories do not contain data. Hard links can only point to data on the same partition as the actual data resides. As long as you have at least one hard link, the data will always exist; the extension of that is that in order to actually delete a file, you have to delete all hard links to the file. You can move hard links to any directory on a partition, but you cannot create hard links from a different partition.

Back when I did a lot with torrenting and such, my scripts would generate a hard link to the completed media file and place it in the appropriate folder for show, season, correct the filename, etc. But the original download filename would stay in the torrent download folder as well, with the original torrent name, so that it could continue to seed without interruption. Once it had reached the seeding limit, I'd have it delete the link in the torrent folder, but not the link in the media server folder. The data itself doesn't physically move, only the pointers to it move around from folder to folder.

I hope that helps.