on the number of sub-folders inside a parent folder that it will backup. For example, I have 700+ subfolders in a particular directory. These are my primary client data folders. They're sorted alphabetically by client name. One weekend I needed to pull a document from a client file to review, and I realized that all the folders with names starting with A through G were backed up, but H through Z were missing.

I went into the office and compared the backup file size with the size of the folder on my computer. Both were identical. So I think iDrive was actually backing my data up, but I was unable to access anything past a certain point. I hope that if I had to have done a system restore from my backup, the missing 400+ H through Z folders would have shown up, but I'm not 100% sure. That's when I moved to Acronis True Image.

IDrive has a phone app that can let you view your backed up files in the cloud. Once you get your backup completed, use the app to view the backed up data to ensure everything is there (if you can tell). If you have any data folder that has a huge number of sub-folders in it, pay particular attention to those files.