Storage on the CacheDrive is used as a cache to improve file access performance.  It does not need to hold the entire dataset at one time and will dynamically adjust its contents based on your usage.  Because of this, any size of CacheDrive can be used with any size of cloud dataset.

For example:

You have 10TB of data and a 1TB CacheDrive. 

You would have access to the entire 10TB in the cloud through the CacheDrive with the most recently used 1TB of files locally stored in your CacheDrive.  If the cache is full, the CacheDrive will remove the least recently used data to make room for newly accessed data.