I'm looking for a cloud backup service. In other words, I already do external hard drive backups but I'd like to also have a cloud-based backup. So I don't want iCloud or DropBox that aren't true backup services (they are syncing services). I've read an extensive article about services like iDrive, CrashPlan, and Backblaze but all these services were tested on Windows; I want to know what Mac users would recommend. I also only want to back up certain folders, not my entire HD.