If you only need one reason to run an OS X Server, then the caching service is it. This is a must service for any company who utilises Apple devices. For an understanding of the caching service please see these two articles: Part 1 and Part 2.
With version 5, Apple have added some extra capabilities, which is the ability to cache iCloud content for iOS 9 and OS X 10.11 clients.
So as well as caching System Updates, App Store apps and iBooks etc, it will now cache personal data from your iCloud Drive and photos. The data is encrypted so only the requesting device can access it, the sever has no access to this data.
This extra caching is designed where you have users with multiple devices sharing the same documents over iCloud.
If you have multiple caching servers, the caching server will try and direct the user to the same server thus minimising what gets cached over all the servers. Obviously more data will get cached so you may need to think about adding more storage or more servers to the network but the caching service is really good at ageing out old data to free space up.
There is no UI to disable just the iCloud piece but there are some undocumented preferences you can set to achieve this
- You can disable the iCloud caching with this command:
sudo serveradmin settings caching:AllowPersonalCaching = no
- You can set a limit on how much is cached with this command, 10GB for example:
sudo serveradmin settings caching:PersonalCacheLimit = 10000000000