The Mac user’s guide to mass storage

Take Control of
Your Digital Storage

Second Edition
Jeff Carlson

This book demystifies storage on the Mac, from mechanical hard drives to solid-state disks, and covering topics such as network-attached storage (NAS), cloud storage, repairing and managing disks, encryption, filesystems (including APFS), and managing data.

All Take Control books are delivered in three ebook formats—PDF, EPUB, and Mobipocket (Kindle)—and can be read on nearly any device.


As the amount of data we store continues to grow, figuring out where to put it and how to access it becomes more complicated. It’s not just that we need to find space for our increasingly large collections of photos, videos, music, and apps—we want it to be available whenever we need it, and be sure that it’s safe from hackers and thieves.

Every Mac includes internal storage in the form of a hard drive, SSD, or Fusion drive. But you may also have one or more external devices (such as hard drives, flash drives, SD cards, or RAID devices), not to mention network-attached storage (NAS) devices or cloud storage (like Dropbox or iCloud Drive). Making sense of all your options, managing your stored data, choosing new devices or services when you’re running out of space, or even just figuring out what’s where can drive anyone to distraction.

“Highly recommend Take Control of Your Digital Storage from @TakeControl books! Like all their titles, well-written, super easy to understand, with vital, vital information! I learned a ton and I’m only up to page 30! A must read…I used to teach this subject in workshops at Apple and thought I knew it all! But I still learned so much valuable information.” —Lars Hoel

Fortunately, Jeff Carlson has a book with all the answers! After decades of working with Macs and accumulating massive collections of photos and videos, Jeff has pulled together a wide-ranging book about Mac storage that contains just the help you’re looking for. Among many other topics, this book covers:

  • How to choose a new (internal or external) hard drive, SSD, or hybrid drive
  • Determining how much storage space you need
  • What you need to know about APFS, Apple’s new filesystem
  • How to use APFS snapshots (a.k.a. Time Machine local snapshots)
  • Formatting and partitioning disks using Disk Utility
  • How to repair a misbehaving disk
  • RAIDs: what they are and how different types compare
  • How to tell when a hard drive is about to fail, and what to do about it
  • What to do with a hard drive when it has outlived its usefulness
  • When to use a flash drive or SD card
  • How to create and use disk images
  • Deciding among local, network, and cloud storage for various types of files
  • What a personal cloud is and why you might consider using one
  • Strategies for freeing up extra disk space

NAS devices get special coverage, including:

  • Why you might want a NAS
  • How to choose a NAS—and when it’s a better idea than an external hard drive
  • Using a NAS with your Mac for a wide variety of purposes
  • Special considerations when using a NAS for digital photos

Jeff also digs into details about numerous storage-related technologies:

  • How to tell if your third-party SSD needs to have TRIM enabled (and what to do if the answer is yes)
  • How to create a software RAID using Disk Utility or SoftRAID
  • What you need to know about filesystems—and how to choose among APFS, Mac OS Extended, FAT, and ExFAT
  • Why and how to encrypt a disk using FileVault or the Finder
  • Using iCloud Drive’s Optimized Mac Storage feature

If you’ve ever been stumped at the difference between a volume and a partition, need help figuring out whether to buy a big external hard drive or a NAS for extra storage, or wonder whether Apple’s new APFS filesystem is right for your needs, this book will tell you what you need to know.

Jeff Carlson

About Jeff Carlson

Jeff Carlson is a contributing editor of TidBITS, a frequent contributor to Macworld and DPReview, and the author of best-selling books on the Mac, digital photography, and, in earlier incarnations, web design and Palm organizers. He consumes almost too much coffee. Almost.

What’s New in Version 2.0

Storage on the Mac continues to get more interesting. I admit, that’s not the type of statement to open with at parties (I guess it depends on the party), but digital storage is changing and affecting all of us.

In version 1.1 of this book, I noted in “Understand File Systems” how macOS 10.15 Catalina splits the startup drive into two separate volumes, which is important to understand when erasing drives and creating new volumes.

APFS is now the default file system for macOS, and so I’ve expanded the discussion of APFS snapshots (also known as Time Machine local snapshots). Snapshots are similar to backups, but not exactly the same; I describe why and how to take advantage of them in the “Make Backups” section. I also answer the frequently asked question, “What About Using an SD Card for Backups?”

Physical storage is changing, too. The “Solid-State Drives” discussion has been broadened to include more detail on how data is stored. I also talk about NVMe (Non-Volatile Memory Express), a much faster type of solid-state memory compared to the replacement SSDs I originally included in the last edition.

Structurally, it made sense to move “External Drives” into its own section, since prices and form factors of external SSDs are now much more reasonable.

Of course, these topics assume everything is working well. In “Identify a Failing Drive,” I bring up early warning signs and use the app DriveDx to diagnose drive troubles before they become serious.

The section on how to use Network-Attached Storage (NAS) helps to answer why you’d consider a NAS (and discusses the many factors involved in buying and using one).

  • Read Me First
    • Updates and More
    • What’s New in Version.0
  • Introduction
  • Your Digital Storage Quick Start
  • Understand Storage
    • Hard Drives
    • Solid-State Drives
    • External Drives
    • How Much Storage Do You Need?
    • How to Dispose of a Hard Disk
    • RAID
    • Disk Images
    • Cloud Storage
  • Format and Partition Disks
    • Understand File Systems
    • Get Started with Disk Utility
    • Format a Disk and Erase Its Contents
    • Manage Partitions and Volumes
    • Run First Aid
    • Identify a Failing Drive
    • Encrypt Disks
  • Use Network-Attached Storage (NAS)
    • Why You Would Consider a NAS
    • Features to Look for in a NAS
    • Work with Files on a NAS
    • NAS for Photography
  • Manage Your Data
    • Choose Your Own Storage Adventure
    • Free Up Disk Space
    • Make Backups
  • About This Book
    • Ebook Extras
    • About the Author
    • About the Publisher
  • Copyright and Fine Print

Jeff Carlson talks Snapshots on MacVoices

Posted by Joe Kissell on June 12, 2020

Jeff Carlson joined Chuck Joiner on MacVoices in a two-part interview to discuss the APFS snapshot capability in macOS.

In Part 1, Jeff explains what snapshots are, how they relate to Time Machine, and where to find them.

In Part 2, Jeff discusses managing and deleting snapshots, and how they affect Disk Utility.

How APFS in Mojave Affects Digital Storage Choices

Posted by Jeff Carlson on April 22, 2019

Just as the file system under macOS works quietly, without fanfare, so do the preparations for the next update to Take Control of Your Digital Storage. We’re working on fleshing out the book for an update later this year, but in the meantime, I want to note a few areas where the march of technology has surpassed what’s in the current edition.

AFPS Everywhere

With the release of macOS Mojave in late 2018, APFS (Apple File System) is now the default file system for all Macs running the latest system, regardless of what type of storage the computer runs. Previously, APFS kicked in only for Macs running solid-state memory, like current laptop models. The exception was Fusion drives, which combine a traditional mechanical (spinning magnetic platters) drive for mass storage and SSD memory for caching frequently used files and the system itself to improve performance. (See the sidebar on page 57, “Which Filesystem for Which Drive?”)

This change has resulted in mixed performance—many people with iMacs and other computers with mechanical drives are seeing worse performance following the update. I’m hoping Apple is working through these issues, and we’ll see performance parity with whichever macOS update is announced at WWDC in June.

I still recommend formatting external mechanical drives as Mac OS Extended instead of APFS. Time Machine drives must still be Mac OS Extended, too.

APFS is a fascinating, deep change to macOS that should be invisible for most people, and I think it mostly succeeds at that. But when things go sideways, that can do so in weird ways. For example, the way it treats free space differently than before, leading to situations where your Mac reports a lot of available storage but an application sees far less. I wrote about this in a recent Seattle Times column, where the culprit was several invisible snapshots: Try these strategies to free storage on your Mac.

If you don’t yet own the book and are curious about just what I’m talking about, I recommend (a) buying the book!, or (b) read this TidBITS article: What APFS Does for You, and What You Can Do with APFS (and then buy the book!).

As I get further along with the book update, we’ll post more information here.

July 22, 2020—This book is currently up to date, but we may do a small update later this year to cover minor changes in Big Sur.


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