External SSD read speed low through Mac mini USB-A

I've also tested USB3 speeds and, although ~400MB/sec is normal for an SATA 6gb SSD, 48MB/sec is NOT. Both speeds should be about 400MB/sec.

Did you let the speed test run for seconds or minutes? With that app the results are sometimes more realistic if you let the test run at least a minutes so it can do more sampling.

What is really odd is that, in the presence of a true drive problem, it is my experience that the Writes speeds typically suffer more than the Reads.

Are the drives in the enclosures SATA or NMVE SSDs?

You may want to share the data with Crucial for their review.

I always like to purchase USB3 devices which support UASP which helps to provide better performance for USB3 drives (all devices in a direct chain must also support UASP). It is possible one of the other USB devices is causing problems with the transfers. Disconnect all other external devices to see if the performance improves.

You may also want to turn off Spotlight indexing on that external drive while running the speed tests.

Are you running any anti-virus apps, cleaning/optimizer apps, or third party security software which may be interfering with the normal operation of macOS? You can try testing while booted into Safe Mode.

What file system is on the external SSDs?

Are these Crucial SSDs actual external SSDs or did you use a bare SSD and installed it into your own adapter or enclosure? Have you tried using a different USB cable/adapter?

You can check the health of the SSDs by running DriveDx. You will need to install a special USB driver in order to attempt to access the health information of an external drive. Post the complete DriveDx text reports here using the "Additional Text" icon which looks like a piece of paper.

It is highly unusual to see read speeds so slow since it is usually the write speeds which will have the slowest numbers.

What is the exact model of your Mac Mini and version of macOS being used? You can get this information by clicking the Apple menu and selecting "About This Mac".

Thank you! I had a similar problem and removing microSD card from the card port (macbook air) changed reading/writing speed of the external crucial x6 from 40 MB/s to 500/600 MB/s. That is enough for me.

Were these Bus powered Hubs, or do they have their own AC power?

the slow speeds look exactly the speeds one would get with usb2, maybe the hub is usb2 only or somehow defect

As a test change the file size in the settings and compare again although I would guess the issue may still be there. I agree with Allan Jones that your read speeds should be closer to your write speeds.

valevari wrote:

I don't think there's anything wrong with them, when I plug each of them on the USB A ports or T4 ports the read speed is what's expected.

It is interesting that the Sequential Write speed is not listed by Crucial in their product documentation for the X6 SSD.....that usually means it is embarrassing:

https://www.crucial.com/content/dam/crucial/ssd-products/x6/flyer/b2c/crucial-X6-productflyer.pdf

Same for the X8 SSD:

https://content.crucial.com/content/dam/crucial/ssd-products/X8/flyer/crucial-X8-productflyer.pdf

Crucial does list the Sequential Read Speed. I think that says everything. Crucial does make some bad SSDs....the 2.5" SATA BX500 model is another example of an SSD to avoid.....the MX500 series is Ok. Unfortunately Crucial and most other SSD manufacturers can no longer be trusted with the performance of their SSDs since they are no longer listing specific details since they are utilizing different components without changing the part number to reflect the change. This also means SSD reviews are nearly meaningless these days.

I'm starting to believe it's a lot more complex and it has to do on how the USB bus works when attaching hubs and devices with different (slower) speeds.

I make sure all my USB3 devices support the UASP protocol so that the USB3 devices with UASP support will function at their best regardless of the other USB devices connected to the dock/hub. Unfortunately I don't see any mention of UASP support on the Crucial X6 & X8 SSDs.....most manufacturers will mention it if it was supported since it is a good selling point to stand out from others.

https://www.startech.com/en-us/blog/all-you-need-to-know-about-uasp

We have purchased two Crucial X6. They were intended for video recording and editing. We formatted one SSD to Mac OS Extended and the other one to APFS.

We tested them with Blackmagic Speedtest and they performed well: around 750MB/s. But then something strange happened to both drives:

Copying master footage to the drives, we noticed that after a while the speed drops down drastically from 720MB/s to around 50MB/s.

Checking them again with Blackmagic Speedtest, both drives suddenly only performed at around 50MB/s.

You might take this with a grain of salt, but we found the following information in a reddit thread:

https://www.reddit.com/r/techsupport/comments/10awqo0/crucial_x6_portable_ssd_slow_writes_in_real_usage/?rdt=40342

We are trying to get a refund from Crucial.

The USB-A ports on the latest Mac Mini are USB 3.0, which only supports speeds of around 5 Gbits/s.

Your speed test is within expectations for USB 3.0.