Thank you for purchasing through links and ads on this site.
OWC / MacSales.com...
diglloyd Deal Finder...
Buy other stuff at Amazon.com...
Memory Upgrades for 2019 Mac Pro - Save Up to 65% vs Factory Costs

Sizing and Setting Up Your Mac Boot Drive

Last updated 2010-09-06 - Send Feedback
Related: how-to, memory, RAID

How big a boot drive do you need?

My boot drive (system and applications) — 21GB used!

A “boot” drive for the Mac system and your applications can be as small as 10GB for an emergency drive, but 60–120GB is a better idea for most users.

More space allows some breathing room; it’s not worth the hassle of redoing it prematurely when it fills up.

Sleep file needs space too

Sleeping the Mac can require as much space as there is memory for the sleepfile, e.g., 16GB of free space for a Mac with 16GB of memory, so be sure to allow for that.

Virtual memory

On machines with limited memory, virtual memory can also use drive space when the Mac gets low on memory; allow 8GB or so extra.

Protect Your Phone
NuGard KX Case for iPhones and iPads.
Outstanding protection against drops and impact!
Plus, excellent grip for wet hands, cycling, etc.

Separate system and data

The reason the boot volume can be so small is that your important data can and should be stored on a separate drive (on systems that allow this conveniently, such as the Mac Pro).

I store all my important files on a separate Master volume; it’s contains everything critical. The boot drive (I name mine Boot) contains the Mac OS X system, my applications, and my home directory. Even portions of my home direction I relocate to my Master volume (e.g., Mail, Documents).

Mirrored or striped

Your boot volume can be a RAID-1 mirror or RAID-0 stripe with one restriction: a bug in Mac OS X does not allow such a volume to be booted in Safe Mode. Because I’ve never had a need for Safe Mode, and because a clone is a much better alternative anyway, I don’t consider this an issue.

As this was written, my boot drive was a triple-SSD RAID-0 stripe, whose performance maxes out the internal SATA bus of the Mac Pro. While that performance is not needed for the boot drive, I use much of the space for a Scratch partition (a Boot volume and a Scratch volume).

New Mac Pro?

Or iMac 5K or iMac Pro?
Consult with Lloyd ASAP before buying!


System configuration for CPU, GPU, memory, SSD, backup, RAID, optimizing performance, workflow.
For YOUR optimal workflow

Avoid costly mistakes in throwing money at the problem for less performance and/or buying the wrong machine for your own needs!

Remote screen sharing available for RAID, software configuration, etc.

More about 2019 Mac Pro vs iMac 5K vs iMac Pro...

Backing up your boot drive.

Clone it. Then you can boot the clone anytime.


Save the tax, we pay you back, instantly!
View all handpicked deals...

Apple AirPods with Wireless Charging Case (2nd Generation)
$200 $170
SAVE $30

diglloyd.com | Terms of Use | PRIVACY POLICY
Contact | About Lloyd Chambers | Consulting | Photo Tours
Mailing Lists | RSS Feeds | Twitter
Copyright © 2019 diglloyd Inc, all rights reserved.
Display info: __RETINA_INFO_STATUS__