Update server storage planning needs for at least 2017

Originally created by @intrigeri on #11806 (Redmine)

This is basically tails/sysadmin#10851, 2017 edition. See parent ticket for other things that need to be taken into account.

Parent Task: tails/sysadmin#11680

Related issues

• Related to tails/sysadmin#10851
• Related to tails/sysadmin#12008
• Related to tails/sysadmin#12119
• Related to #12469 (closed)
• Related to tails/sysadmin#15780
• Blocked by tails/tails#12002
• Blocks tails/sysadmin#12111
• Blocks tails/sysadmin#13425