You can use the Energy Saver setting in the System preferences in OS X but you may find that the system still manages to invoke a power saving mode, this is especially painful when you require the machine to be fully up for an extended time, for example when running your first synchronisation of cloud storage. So to control the sleep functions of OS X there is a nice terminal command CAFFEINATE, this can be used to keep all aspects of the system live.
For example typing caffeinate -i -d will prevent the system and hard drive from sleeping. When you do not need to have the machine running fully you just CTRL Z the terminal window and quit terminal.
If you go to the following link you will find the help page for this command, https://ss64.com/osx/caffeinate.html.