Q I am attracted by the idea of iCloud, but have been careful not to use it any more than minimally until now. I have a monthly broadband limit at home which could easily be breached if I transferred too much data. How can you control iCloud use?
A Under OS X and iOS, the management features are concerned with the amount of data you have stored in iCloud, rather than the amount which is transferred to and from the cloud. However iOS devices do keep track of mobile data transfers. So although there is no single and simple way of monitoring how much of your monthly limit you have used for iCloud, you can control that.
In OS X, the central controls are in the iCloud pane in System Preferences, where you set which iCloud services you use. Click on the Manage… button at the bottom right, and you can then see the storage use broken down by application, including general iCloud Drive use.
In iOS, controls are in the General app. Mobile Data provides total mobile data usage, and you can then see and limit data usage by each app. iCloud then gives finer control: in Storage, Manage Storage shows the same breadown as under OS X. If you are getting too close to your cap at any time, you can use these controls to limit iCloud use, and remain within your limit. If the worst comes to the worst, you can always sign a device out to stop all iCloud data transfer, although that will limit what you can do, of course.
In practice, most users who do not back up to iCloud remain well within their data limits. Backing up is another issue, though.
Updated from the original, which was first published in MacUser volume 27 issue 25, 2011.