Why Is My External M.2 SSD Slowing Down to 40 Mbps Write Speed

Why is my external M.2 SSD slowing down to 40 Mbps write speed all of a sudden? Did I buy a faulty SSD? Or are there any other reasons that lead to this? Thanks in advance!

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Oliver· Answered on Jun 17, 2024

External M.2 SSDs can experience slow write speeds due to a few potential reasons:

  • Too many fragments on your SSD
  • USB interface limitations
  • SSD runs out of space
  • AHCI mode is disabled
  • Corrupted SSD

To accurately check your SSD write/read speed, you can use EaseUS Partition Master Free, which also offers the "4K Alignment" feature that can help improve your SSD performance.

Free Download 

Windows 11/10/8/7100% Secure

You can follow the steps here to check the SSD speed first:

Step 1. Launch EaseUS Partition Master and go to the Discovery tab.

Step 2. Select the "DiskMark" feature and then choose the target drive, test data, and block size.

Step 3. Click "Start" to run the disk test, and you will see the Sequential or Random read/write speed, I/O, and Delay data.

After checking the SSD speed, follow the steps here to perform 4K Alignment and improve SSD read and write speed:

Step 1. Go back to EaseUS Partition Master and go to the Toolkit tab.

Step 2. Select the "4K Alignment" feature and then choose your SSD.

Step 3. Click "Start" and wait patiently.

Related Article: How to Fix SSD Slow Write Speed on Windows 10/11 [Full Guide]

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