Question Could someone explain these low read/write speeds from my new external ssd?

infinitedrive06

Junior Member
Feb 6, 2023
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I will try to post the info as detailed as possible.

Started around 350MB/s which I thought was low to begin with and then almost halfway through shot down to 30MB/s and has been sitting there.
I did my research before buying and I know its a QLC SSD, but after this write, I will only be using it to copy to other computers.
I knew I wouldn't hit top speeds writing to the drive but I didn't think it would be moving slower than my USB flash drives...


Copying 575GB FROM MY PC: Crucial P3 1TB 3D NAND Flash PCIe Gen 3 x4 NVMe M.2 Internal SSD Read Speed: Up to 3,500MBps / Write Speed: Up to 3,000MBps

FROM PORT: USB 3.1 Gen 1 (up to 5Gbps) USB-C Port in motherboard in back of computer

WITH CABLE: Type-C to Type-C USB cable (10Gb/s)

TO: Crucial X8 External SSD USB 3.2 (Gen 2 Type-C) Read Speed Up to 1,050MBps / Write Speed Up to 1,000MBps

Edit: Now I'm copying the same 575GB from that External drive to a laptop and getting similar results.
Laptop has a Thunderbolt 3 port and it's copying to a 1TB Sata SSD with a 500MB/s read / 450MB/s write spec.
Was around 500MB/s for about 60% of the way and then dropped down to around 5-7MB/s that occasionally will jump up to 175ish for a few seconds and then back down.


Thanks in advance.
 

Tech Junky

Diamond Member
Jan 27, 2022
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Depends on a few things
Drive
enclosure
File types and sizes
Single vs multithread

Bulk single copies tend to slow down in Windows but, your bottom speeds are really slow and might just be the lack of buffer on the drive. but could be a temp issue though too. If you monitor with CDM during transfers you can easily figure that out.

On my TB with Acasis and sn770 I can get it to 3GB/s. With other drives they're slower at 2GB/s. Those other drives though internally hit 3-5GB/s.
 

infinitedrive06

Junior Member
Feb 6, 2023
2
0
6
Depends on a few things
Drive
enclosure
File types and sizes
Single vs multithread

Bulk single copies tend to slow down in Windows but, your bottom speeds are really slow and might just be the lack of buffer on the drive. but could be a temp issue though too. If you monitor with CDM during transfers you can easily figure that out.

On my TB with Acasis and sn770 I can get it to 3GB/s. With other drives they're slower at 2GB/s. Those other drives though internally hit 3-5GB/s.

My PC also has 2 teal USB-A Ports (USB 3.1 Gen 2 [up to 10Gbps]) - I was made to believe I would have better speed transfers with the USB-C - USB-C cable, but would the speeds be better if I put the adapter on and plugged into the teal USB-A?
 

Tech Junky

Diamond Member
Jan 27, 2022
3,282
1,086
106
I use adapters too in order to thin out the cable inventory.

The adapters aren't all the same though as I found from testing a handful of them from micro/mini/A/C depending on what I was connecting to.

It took a couple of tries per connection to find the right adapter to hit the speed I was looking for or in some cases the voltage I was trying to charge devices with.

For a C<>A I use - https://www.amazon.com/gp/product/B07YCZ2S82

Some are hit or miss in how they perform though even though there really isn't much to them that should affect the performance. However, some are wired to USB2 and others are wired to current spec USB3.2. The same goes for cables as well some only do 480mbps and others can hit 20gbps unless you go TB and then it still varies by cable.
 

solidsnake1298

Senior member
Aug 7, 2009
302
168
116
It depends if that 575GB are a few big files or a lot of small files. Correct me if I'm wrong, but I'm pretty sure that Windows (I'm assuming you are on Windows) file copy is single threaded. Regardless of who fast your drives or CPU are, Windows suuuuucks at copying lots of small files.

I've made backups of my user directory, copying it from my NVMe OS drive (Samsung 970 EVO at the time) to my SATA SSD (Samsung 860 EVO), and it took over 15 minutes to copy 200,000 files, but only 50GB in size. During the period where it looked like it was working through a lot of small system files, the data rate dropped into the sub 1MB/s range. If that was a single 50GB file, 15-20 seconds max.

Windows file copy sucks.