Simplifying Mirrored and Striped RAID Sets on macOS

Introduction

Over the past weekend, a friend asked me to set up a backup drive to protect their essential data. They wanted a traditional Time Machine disk to mirror their startup disk. I suggested a mirrored RAID set using the Apple-supplied Disk Utility that comes with macOS. Setting up a mirrored drive is straightforward with Disk Utility and creates a complete backup of the drive it mirrors. This guide will walk you through the process of setting up both mirrored and striped RAID sets.

What is RAID?

RAID (Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units. The primary types of RAID discussed here are:

• RAID 1 (Mirrored RAID Set): Provides redundancy by duplicating the same data on two or more disks.
• RAID 0 (Striped RAID Set): Enhances performance by splitting data across multiple disks.

Setting Up a Mirrored RAID Set (RAID 1)

Prerequisites

Before you begin, ensure you have:

• A backup of your data using Time Machine.
• At least two drives to create the RAID set.

Steps to Create a Mirrored RAID Set

1. Open Disk Utility: Navigate to Applications > Utilities > Disk Utility.
2. Select the Disk: In the left-hand column, select the disk you want to mirror and click RAID.
3. Configure RAID:
   • Name your RAID set.
   • Select the format you want to use.
   • Set RAID type to Mirrored RAID Set.
   • Click the + button to add the RAID set.
4. Set Options:
   • Highlight the RAID array you just added and click Options.
   • Set the block size (32k is a general recommendation).
   • Choose whether you want the RAID set to automatically rebuild itself (recommended).
   • Click OK.
5. Add Drives:
   • Select a drive from the left-hand side of the Disk Utility panel.
   • Drag it over the new RAID array you created.
   • Add at least two drives to your array.
6. Create RAID Set:
   • Click the Create button.
   • A warning window will remind you that all data on the drives will be erased.
   • Click Create to finalize the RAID set.

You have now created a mirrored RAID 1 set.

Setting Up a Striped RAID Set (RAID 0)

Steps to Create a Striped RAID Set

1. Follow Steps 1-3: As outlined in the mirrored RAID set section, but select Striped RAID Set as your RAID type.
2. Add Drives:
   • Drag the drives you want to use into the RAID array.
   • Ensure you have at least two drives.
3. Create RAID Set:
   • Click the Create button.
   • Confirm the warning about data loss.
   • Click Create to finalize the RAID set.

Creating a Mirrored Striped Set (RAID 10)

Steps to Create RAID 10

1. Create Two Striped RAID Sets:
   • Name one Set1 and the other Set2.
   • You will now have two drive images, each representing a striped RAID set.
2. Create a Mirrored RAID Set:
   • Name the array Macintosh HD.
   • Add the components of the mirror by dragging Set1 and Set2 disk images into the new RAID array.
3. Finalize RAID 10:
   • Click Create.
   • Confirm the warning about data loss.
   • Disk Utility will create the mirrored striped set, and you will see a new disk image named Macintosh HD.

Benefits of RAID 10

RAID 10 combines the benefits of RAID 0 and RAID 1:

• Performance: Data is striped across multiple drives, enhancing read/write speeds.
• Redundancy: Data is mirrored, providing a backup in case one set fails.

Interesting Stats

• According to a Backblaze report, the annualized failure rate (AFR) for hard drives in 2021 was 1.01%. Using RAID configurations can significantly mitigate the risk of data loss.
• A study by Seagate predicts that by 2025, the global datasphere will grow to 175 zettabytes, emphasizing the need for efficient data storage solutions like RAID.

Conclusion

Setting up RAID configurations on macOS using Disk Utility is a straightforward process that can significantly enhance your data security and performance. Whether you opt for a mirrored RAID set for redundancy or a striped RAID set for performance, this guide provides all the steps you need to get started.

For more detailed information on RAID arrays, visit the Apple Support page.

By following these steps, you can ensure that your data is both secure and easily accessible, providing peace of mind and improved system performance.