Disk Utility: The Complete Mac Guide

Introduction

Disk Utility is one of the most important tools on your Mac. It helps with managing, repairing, and diagnosing your hard drives and SSDs. Here you'll learn everything about this powerful tool.

What is Disk Utility?

Disk Utility is a built-in macOS application for:

• Managing hard drives and volumes
• Formatting and partitioning
• Error diagnosis and repair
• Creating disk images
• Data recovery preparation

Where to find it?

• Applications → Utilities → Disk Utility
• Or: Spotlight search (Cmd + Space)

Main Functions Overview

1. First Aid

Checks and repairs disk errors:

• File system errors
• Directory structures
• Permissions
• Volume integrity

2. Erase/Format

Supports various file systems:

• APFS (recommended for SSDs)
• Mac OS Extended (HFS+)
• ExFAT (Windows-compatible)
• FAT32 (older compatibility)

3. Partition

• Add/remove volumes
• Resize
• Different file systems
• Create boot partitions

4. RAID Configuration

• RAID 0 (Striping)
• RAID 1 (Mirroring)
• JBOD (Concatenated)

Solving File System Problems on Mac: A Guide for Beginners and Advanced Users

File system problems can lead to symptoms like unexpectedly quitting programs, corrupted files, unresponsive external drives, or even a non-starting system on Mac. macOS provides a powerful tool with Disk Utility to diagnose and fix many such problems.

Basics: Using Disk Utility for Troubleshooting (Beginners)

The Disk Utility is the standard graphical app in macOS for managing hard drives, SSDs, and volumes. It can check the formatting and file system structure of a drive and automatically repair certain errors.

Typical problems it can solve:

• Multiple apps crash frequently
• Files won't open or are corrupted
• An external device isn't working properly
• The Mac won't start

Opening Disk Utility:

You can find the app under Applications → Utilities or via Spotlight search for "Disk Utility". Launch the app and first make sure you have enabled the "Show All Devices" option in the menu bar under View.

Running "First Aid":

Disk Utility offers the First Aid button to check and repair a selected volume's file system. Proceed in this order:

1. Volume Check:
First select a volume (partition) in the sidebar where you suspect errors (e.g., Macintosh HD – Data). Click First Aid and confirm with "Run". Run this First Aid sequentially for all volumes of the affected drive.

2. Container Check (for APFS):
If the drive is partitioned in APFS format, next check the APFS container. Select the parent container in the sidebar and run First Aid again.

3. Physical Drive:
Finally, you should – especially for HFS+ (Mac OS Extended) formatted disks – check the entire drive. Select the top element (the physical disk) in the sidebar and click First Aid.

If "First Aid" Doesn't Help:

If Disk Utility cannot repair an error, it usually recommends backing up the data and reformatting the drive. If it fails once, first try a second run of First Aid. If the error persists, you should rescue important data from the drive (if still possible) and format the drive.

Advanced: Repair and Formatting with Terminal (diskutil)

For experienced users, macOS offers diskutil, a powerful command-line tool that enables deep control over hard drives and volumes. Many Disk Utility functions are also available in Terminal – sometimes with more detailed information and additional options.

Useful diskutil Commands:

Display Drive Overview:
Run diskutil list in Terminal to list all detected disks and partitions:

$ diskutil list
/dev/disk2 (external, physical):
 #: TYPE NAME SIZE IDENTIFIER
 0: GUID_partition_scheme *2.0 TB disk2
 1: EFI ⁨EFI⁩ 209.7 MB disk2s1
 2: Apple_HFS ⁨Data⁩ 1.8 TB disk2s2
 3: Apple_HFS ⁨Backup⁩ 249.7 GB disk2s3

Check or Repair Volume:
Similar to the graphical "First Aid", you can perform file system checks with diskutil:

# Check "Data" volume for errors (without repair)
diskutil verifyVolume /Volumes/Data

# Repair the same volume (run with admin rights)
sudo diskutil repairVolume /dev/disk2s2

Format Drives and Partitions:
With diskutil you can flexibly erase, partition, and format disks:

# Format external SSD on disk3 to APFS format
sudo diskutil eraseDisk APFS "NewSSD" /dev/disk3

Disk Utility vs. Terminal (diskutil):

APFS vs. HFS+: Peculiarities in Repair and Formatting

Since macOS 10.13 High Sierra, Apple uses a new file system called APFS (Apple File System) as the standard for SSDs, while previously Mac OS Extended (HFS+) was the standard. Both file systems differ not only in structure and features but also in aspects of maintenance and repair.

Modern Design vs. Proven Tools:

APFS brings advanced features that HFS+ doesn't have – such as snapshots, copy-on-write metadata, shared free space in containers, file cloning, and much more. This architecture is designed to increase reliability.

Differences in "First Aid":

APFS volumes often lie in containers: Apple recommends checking first all volumes, then the container, then the physical device. A specific annoyance with APFS is the unmount problem of First Aid. If First Aid aborts with an error message on an APFS volume, it's worth trying again in Recovery Mode or via Terminal.

Interestingly, these unmount errors don't occur with HFS+ volumes – here the old architecture seems easier to handle.

Performance and Maintenance Aspects:

APFS conceptually dispenses with defragmentation – on an SSD fragmentation isn't a big issue, but on a rotating hard disk (HDD) APFS can lead to severe fragmentation, especially of file system metadata, which significantly degrades performance.

If a Mac still uses an HDD (such as in older iMacs), HFS+ may be more performant under certain circumstances, while APFS shows noticeable disadvantages there.

Compatibility and Use Cases:

HFS+ remains relevant for compatibility cases – e.g., when you exchange a drive between macOS and older OS X versions. APFS is mandatory for macOS boot volumes from Big Sur onwards and is required by current Macs.

For external drives, you have a choice: For fast SSDs, APFS is usually sensible, for purely mechanical hard drives with certain usage profiles, HFS+ can have advantages.

When Professional Help is Needed

Contact us for:

• Repeated First Aid errors
• Unrecognized hard drives
• Clicking sounds from HDD
• After water damage
• Important data without backup

Conclusion

From a user perspective, not much changes in daily use with APFS – Disk Utility works similarly, except that you encounter APFS volumes in containers. The pitfalls lie under the hood: APFS is designed more modern and secure, but has (still) less support from third-party tools.

What remains important in both worlds: Make backups! Neither APFS nor HFS+ can always catch hardware failures or severe logical errors, and especially with APFS, you have hardly any repair alternative in an emergency without backup.

Disk Utility is a powerful tool – used correctly, it can solve many problems. For uncertainties or serious errors, we're here with professional support!

Stuck with Disk Utility errors?

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