Acronis 2016 Question

Yes, when it says "entire PC" it mean all the drives on your PC.  Of course, the more data you have, the bigger the space required for the resulting image or direct backup.
 
I'm not sure why it would default to that, since I would think most people are backing up their system partition/drive.

I use Acronis 2017. I recommend that you create backup profiles for whatever it is you need. 
For example, I have a mirror backup of my C drive's operating system. I then have a backup of "My Documents". 
Then I have a backup of all my song/DAW/project files. 
Each backup goes to an external USB drive and to the Cloud. 
 
You should know what and how your backups are being created and saved. 
Acronis support can help you get setup. 
 

I tend to have different backup stratagies for different data types, sometimes disc image, sometimes file backups so I do not use the "whole PC option". I also feel (maybe wrongly?) that the bigger the backup file the more likley it will corrupt. For projects and other fast changing data I also mirror on my network drive using synctoy in addition to the Acronis backups.
 
I try to have redundant backups. One to local USB discs and one to a network drive in a different building, the latter is a bit slow but its insurance against theft or other disaster in the studio.
 
Synctoy does not handle my large Kontakt library collection well, its too big, as it represents my biggest investment so I keep a manual mirror of this on the network drive in addition to the Acronis backups.

i usually don't install acronis, instead make a disk and boot from that when i back up, keeps any extra running processes etc out of the picture and don't have to bother disabling them, i rather have nothing not associated with music on my daw pc's. don't need any automatic backup stuff, using ti2017 now, do full backups every time

Thanks for these tips. I like the idea of backing up the individual folders that are the most important in addition to  a "master" back up.
 
 I can understand the apprehension in keeping all of those eggs in one basket. I'm considering a dual approach. When I used Acronis in the past, it stored all system backups as separate files. I would go into the backup drive and remove the older ones to make room for the more recent. Not sure if the 2016 version makes additions or writes entire new files each time.  If Acronis  only updates an existing image I see this as being more efficient.
 
I would like to make copies of the main files in an un imaged format so that I could simply save them to new drives if replacing a computer.