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Some data you have is so important that if you lost it you would have a severe hardship. For example I have an encrypted file that contains all my passwords, banking and other important data in it. Encryption means that no one can access it without the password, but I can't afford to lose that file either. In addition, I have scans of birth certificates and other important documents. Offsite storage of irreplaceable data such as this can bring great peace of mind.

Yes, you can make backups of your data onto an external hard drive and take that hard drive off site (and depending on the importance of your data, maybe you should) but that requires regular action on your part. iDisk, on the other hand, is completely transparent offsite storage.

iDisk, which is part of MobileMe, looks and acts just like a hard drive in the Finder. When you save documents to your iDisk, they are immediately synced to Apple's servers somewhere (protected inside a mountain in Colorado? Who knows.) That means that you have offsite backup of that document without you having to do anything.

Your iDisk does have two disadvantages, one of which you can take care of in the iDisk tab of the MobileMe System Preferences pane:

• Your iDisk is only 20 gigs in size. That is pretty small for a hard drive. This means you can't store everything on your iDisk. It isn't suitable for your iPhoto Library for example. But it is plenty large enough to store your most important documents.
• iDisk requires that you have internet access. If you have a notebook Mac, you might not always be connected to the internet. You can solve this issue by turning on iDisk Sync in System Preferences. With iDisk Sync, you have a local copy of your iDisk that is stored on your internal hard drive as well has an offsite copy. Any changes you make to your iDisk are written to the local copy first and then synced to the offsite copy. This not only speeds up access to your iDisk, but also means that you don't need to be connected to the net to access your documents.

If you should ever lose or damage your Mac, you can go to any web browser on any Mac or PC and go to www.me.com and you will have immediate access to your iDisk.

If you want more transparent off-site storage to back up your entire User folder or hard drive, check out this tip on off-site backups.

Related Items: Security Series | iDisk | dot Mac | Backups