A couple of days ago I came across this excellent tip to download your GMail mail to your computer with IMAP. Before you continue reading here, I assume you read that article first. In this article, the path /path/to/gmail/backup is the path of the local repository, which you configured for offlineimap.

In the comments of that article, I stated that there's a problem with duplicate files. GMail has no real folders, but you can label e-mails. This implies that the same e-mail may possibly end up in more than one folder. When you download all folders, it is likely you store that e-mail multiple times.

Given the (ever increasing) storage size of a GMail account, it becomes interesting as an alternative backup storage location. The GMailFS project becomes an interesting option then.

Using Gentoo, I referred to Gentoo-Wiki.com where a howto was given on how to install GMailFS. This is a virtual file system, based on the FUSE infastructure. This allows you to enable support for a (virtual) filesystem without having to modify the kernel.