Windows 10: USB Flash drive - very slow writes, but read speeds are fine

Suddenly one of my USB Flash drives has become very slow to write to. I'm seeing 'peak' write speeds measured in KB/sec, not MB/sec. However, there are no write errors, and once written files can be read at normal speeds. All my other USBs work normally, just this one is slow, and it's the same in every PC and OS I have, Win10 or Win7. Obviously there's something very wrong with this particular PNY 32GB USB 2.0 flash drive. But intriguingly it passes every test I can throw at it, bar the write speed. I have installed Ventoy on it and added ISOs for Minitools bootable Partition Wizard 9.1 and Windows 10 21H1, the latter taking over 20 hours to copy!. But both boot successfully. And when I booted Partition Wizard from this USB, its surface check of the USB then said 100% good. I've never has a USB fail on me before, and certainly not heard of one failing like this. I'm not looking for repair suggestions, I'll dump this USB soon. But I'm intrigued, can anybody suggest a test that will reveal what's actually gone wrong?

:)

 

Slow HDD read and write speeds

Hi,

Thank you for writing to Microsoft Community Forums.

We will require a few more information from you to help you further with the issue. Please reply with the following details:

• In which device are you facing this issue?
  
• Are you using an external HDD or internal HDD?
  
• Are you getting the read and write speed issue on any particular application?
  

However, you can Disk Defragment on your computer to optimize the drive. To run Disk Defragment please follow the steps from the article

Defragment your Windows 10 PC.

Alternatively, you can check for the read and write speed of the HDD in task manager. Please follow the steps mentioned below to check the read and write speed of the hard drive:

1. Press Ctrl + Shift + Esc key together on the keyboard.
   
2. Click on Performance tab.
   
3. Click on Disk 0.
   
4. You will find the Read speed and
   Write speed at the bottom of the window.
   

Hope it helps.

Please reply with the status of the issue, we will be glad to help you further.

Nikhar Khare

Microsoft Community - Moderator

 

RANDOM read and write speeds too low

Two USB 3.0 drives and a USB 3.0 flash drive have reasonable to good sequential read and write speeds. But the RANDOM write and write speeds are awful, up to 200 times slower than the sequental speeds. I test with DiskMark from CrystalDiskMark. I
tested both with drives directly connected to PC 3.1 USB port and via a 3.0 USB Hub.

Results:

Seagate USB 3.0 Disk drive: Sequential read approx. 140 MB/s, Sequential write approx. 140 MB/s, Random read around 1 MB/s, Random write around 1.9 MB/s

My Book USB 3.0 Disk drive: Sequential read approx. 230 MB/s, Sequential write approx. 38 MB/s, Random read around 1.5 MB/s, Random write around 2.2 MB/s

Sandisk Extreme GO USB 3.1 Flash Drive: Sequential read approx. 190 MB/s, Sequential write approx. 140 MB/s, Random read around 7 MB/s, Random write around 2.5 MB/s

Since this happens on different devices my guess is the problem is with the computer and not with the devices. For each of these devices the policies are set for faster performance.

Drivers are the best Windows can find (when updating drivers via Device Manager).

What can I do to resolve the very slow RANDOM read and write speeds?

 

Flash drive reads/writes at inconsistent speeds

I work on a lot of large .rtf files in Office. Sometimes when I click _Save_, the window freezes and gives me a loading wheel for 10 or 15 seconds before the document finally saved. Sometimes (less often) the file saves almost instantly. It's completely
unaffected by how many changes I have made or even how large the document is--when the drive is in 'slow' mode, even a 50kb plain text file will take several seconds to save. It also isn't affected by any running processes that I can see--does the same thing
in both Windows 10 and Windows 7 and regardless of what computer I use, etc. This read/write inconsistency also happens while copying/moving files to or from the drive. In 10 where the speed display is more accurate, it speeds up and slows down a lot. It goes
as high as about 5mb/s at times, but averages at an absurdly slow speed (something like 1-200kb/s. Please don't tell me 'Flash drives are slow.' They're not
that slow.) The speed seems to have no patterns based on the type or size of file currently being copied/moved. Does anybody have any idea why this could be?