What kind of links (symbolic, hard, junction pts...) for multiple cloud backups?

Question

Google-Drive's MS-Windows software doesn't follow links of any kind. Dropbox and Skydrive both - apparently, follow links. I am using MS-Windows7 64-bit professional edition.

What I did was to move my main work directory into Google-Drive's folder, and created symbolic link to it, in it's original path in C:. This was based on a blog post a read. However, I plan to also keep my work backed up in Dropbox (or Skydrive), so I was thinking of creating a symbolic links to the work directory inside Google-Drive folder, in Dropbox's folder.

However, while reading up about mklink command that is used to create the links, I realized that there are 3 kinds of links, i.e.

• Symbolic links
• Hard links
• Junction points

On reading up a bit more, and drawing parallels (at least for Symbolic and Hard links), to the POSIX equivalent, I think I should be using Hard-links instead, and not Symbolic-links. This is because, I do not want an inadvertent "delete" of the physical directory inside Google-Drive folder, to invalidate the other 2 symbolic links (which would happen given the very nature of those type of links). Hard-links would use reference counting, and won't delete the directory from filesystem, until the last link is deleted. Am I correct in my thinking ? I've not understood Junction points too well, and it's advantages over the other two types, to appreciate whether or not to consider it.

Answer 1

I'm not sure you have quite got things straight. Here is my take on the 3 in laymans terms.

Junction Points are the original feature of HPFS (prior to NTFS) and are similar to Hard Links.

Hard Links can only be made between folders on the same drive and the link is identical to the original. That is to say, if you delete the link, you've deleted the original.

Soft Links are defined rather higher up in the OS and require better software support, at least in Windows. Deleting a soft link will leave the original in place.

The most transparent to applications is likely to be Junction Points, followed by Hard Links and lastly soft links.

In any case, you still need to be wary of how applications and the OS interact with linked files (shouldn't be so bad with linked folders). Given that Windows is not above doing some nasty corruption of you files, linking folders does make things a little worse. You also need to be aware of what happens when doing copies and backups using software that may not fully understand your links. For example, when backing up the original and the linked folders, you probably want to exclude the linked location or would want the option to backup (and appropriately restore) the link not a copy of the file.

Although links are very common under UNIX like OS's, they are not so common under Windows and therefore have patchy support as you have already seen. Indeed, so patchy that often Microsoft themselves don't use them but instead mess around in the registry to create pseudo links (see Library documentation in Windows).

Hope this clarifies! If not, leave a comment and I will try to update.