External SSD on Mac Really Slow: Quick Fixes

Key Takeaways

A slow external SSD on a Mac can be due to incompatible file systems, connection types, or outdated macOS settings. Optimize speed by selecting the correct file system, using compatible connection types, and testing for potential hardware issues.

Using an external SSD on your Mac can significantly improve storage performance, but sometimes, users encounter frustrating slowdowns.

This article will guide you through diagnosing, optimizing, and resolving common issues that cause external SSDs to perform slowly on macOS devices.

We’ll cover reasons for reduced speed, solutions for improving performance, and crucial settings that can make a real difference.

External SSD on Mac Really Slow: Common Reasons 

External SSDs can deliver impressive speeds, but several factors may cause performance to lag. Here are some of the most common reasons:

1. File System Compatibility

An external SSD formatted in NTFS (common with Windows) won’t perform as efficiently on a Mac. While Macs can read NTFS, they may not fully utilize the SSD’s potential due to compatibility constraints.

2. Connection Type Limitations

The speed of an external SSD largely depends on the connection type—USB-C, USB 3.0, Thunderbolt, etc. Older connections can bottleneck the SSD’s speed.

3. macOS Settings and Background Tasks

macOS has background processes, such as indexing or backups, that may impact the SSD’s performance, particularly when performing intensive tasks.

4. Fragmentation and Storage Management

Though SSDs aren’t as impacted by fragmentation as traditional HDDs, excessive data storage can hinder performance over time.

How to Diagnose Slow External SSD on Mac?

Understanding the root cause of slow speeds is essential to finding a solution.

Here’s how to effectively diagnose issues with your SSD.

1. Check Connection Type

Ensure the external SSD is connected via an optimized port, such as Thunderbolt or USB-C.

Avoid using older USB-A ports that may limit transfer speeds.

2. Run Activity Monitor

Using the Activity Monitor app on macOS, observe if any processes are consuming excessive system resources.

High CPU or RAM usage may indicate other processes slowing down your SSD’s performance.

3. Analyze Disk Space

Check your SSD’s available space in Disk Utility.

If the drive is almost full, consider freeing up space, as SSDs require some free capacity to operate efficiently.

4. Run Disk Speed Tests

Use apps like Blackmagic Disk Speed Test to assess your SSD’s read and write speeds.

This test helps you identify whether your SSD’s speed aligns with its advertised performance.

Optimal File System for External SSDs on Mac

Choosing the right file system is critical for achieving optimal SSD performance on macOS.

1. Recommended File Systems

• APFS (Apple File System): Optimized for macOS, APFS is the default choice for SSDs and provides high-speed read/write performance.
• exFAT: If you use the SSD across macOS and Windows, consider formatting it to exFAT. It doesn’t perform as efficiently as APFS but is compatible with both OSs.

2. How to Format SSD to APFS

1. Connect your SSD to your Mac.
2. Open Disk Utility.
3. Select the SSD and choose Erase.
4. Choose APFS as the format and proceed.

Note: Formatting will delete all data on the drive, so ensure to back up any important files before proceeding.

Impact of Connection Type on External SSD Speed

The connection type directly impacts the SSD’s potential speed.

Here’s a comparison of common options:

1. Thunderbolt vs. USB-C

• Thunderbolt: Offers up to 40Gbps speed, ideal for high-speed SSDs.
• USB-C: Although USB-C ports can handle speeds up to 10Gbps, many external SSDs with USB-C connections max out at 5Gbps.

2. Using the Right Cables

To achieve optimal speeds, always use certified Thunderbolt or USB-C cables.

Inferior or incompatible cables may significantly reduce performance.

3. Avoiding USB Hubs

Connecting an SSD through a hub, especially one with multiple devices, can create a bottleneck.

Direct connection is preferred for maximum speed.

macOS Settings to Improve External SSD Speed

macOS provides several settings that can help improve your SSD’s performance.

Let’s look at some adjustments you can make:

1. Disable Spotlight Indexing

Spotlight indexing can slow down the SSD, especially if it’s constantly searching and updating files.

• Go to System Preferences > Spotlight > Privacy.
• Add your SSD to the list to stop Spotlight from indexing it.

2. Manage Time Machine Backups

If your SSD is used as a Time Machine backup drive, macOS may slow performance when it runs background backups.

• Consider using a dedicated drive for Time Machine backups or temporarily disabling automatic backups in System Preferences.

3. Adjust Energy Saver Settings

• In System Preferences > Energy Saver, uncheck “Put hard disks to sleep when possible.” This setting may affect SSDs, leading to slower performance when the drive is idle for extended periods.

How to Test and Benchmark External SSD Speed on Mac?

Benchmarking the SSD is essential to understand how it performs. Here’s a step-by-step guide:

1. Use Blackmagic Disk Speed Test

• Download and open the Blackmagic Disk Speed Test from the App Store.
• Select your SSD as the test drive and run the test to observe read and write speeds.

2. Compare Results with Expected Speeds

• Check your SSD’s specifications (available on the manufacturer’s website) and compare the advertised speeds with your test results. Any significant difference may indicate a problem.

3. Monitor Speed Variations

Run multiple tests to see if the SSD performs inconsistently. Sudden speed drops may signal intermittent issues related to hardware or connection.

Common Hardware Issues Causing Slow SSD Performance

If your SSD is still performing poorly, hardware issues might be the culprit.

1. Loose or Damaged Cables

Loose or damaged cables can create intermittent speed issues. Test with a different, certified cable to confirm the source of the problem.

2. Overheating

External SSDs can slow down significantly when they overheat. Make sure the SSD is well-ventilated and not used for prolonged, intensive tasks without breaks.

3. Drive Age and Health

All SSDs have a limited lifespan. Use Disk Utility to check the drive’s health. If the drive shows signs of wear, it may be time to consider a replacement.

Firmware Updates and Drivers for External SSDs

Firmware updates and drivers can optimize your SSD’s performance and fix bugs that may be causing slowdowns.

1. Check Manufacturer’s Website

Visit the manufacturer’s website to see if any firmware updates or drivers are available for your SSD model.

2. Use Vendor-Specific Software

Some manufacturers provide their software for updates, such as Samsung Magician or SanDisk SSD Dashboard. These programs often help with firmware updates and performance checks.

3. Update macOS

macOS updates can also include patches that improve external SSD compatibility and performance. Always ensure your Mac is running the latest version of macOS.

FAQs

Q1: Can formatting an external SSD improve its speed on a Mac?

Yes, formatting to a macOS-optimized file system like APFS can help maximize speed and compatibility.

Q2: Why does my SSD slow down after connecting to a hub?

Hubs can limit bandwidth, especially when multiple devices share the same connection, reducing the SSD’s speed.

Q3: Does using an old USB-A port affect SSD speed?

Yes, USB-A ports generally have slower data transfer rates than USB-C or Thunderbolt, which can hinder your SSD’s performance.

Q4: How often should I update SSD firmware?

Check for firmware updates periodically, especially if you notice a drop in performance or the manufacturer releases a new version.

Q5: Can too many background apps slow down my SSD?

Yes, macOS background apps and indexing can use system resources that impact SSD speed. Regularly monitor and manage background processes.

Conclusion

An external SSD on a Mac can provide lightning-fast storage, but only when configured correctly and paired with compatible hardware. 

If you experience slow speeds, start by diagnosing connection types, adjusting macOS settings, and ensuring your SSD uses an optimal file system like APFS.

Regular testing, firmware updates, and proper cable use can further enhance performance. 

With the tips in this guide, you’ll be able to maximize your SSD’s speed and enjoy a smoother, faster experience on your Mac.