If I use the iDrive local backup it is on a USB drive and, by the nature of such devices, it can be painfully slow. What I would like is to have more than one local backup. With two I could have one for all the files that change infrequently, so the updates could be similarly infrequent, and one for frequently changed files which I could update frequently.
The software that I currently use for local backups, GFI Backup 2009, can easily create as many independent backups as you wish. It works without problems but, unfortunately, it is no longer supported by GFI so I really should be looking for an alternative.