I’ve been doing some speed tests with my SSDs on a Mac mini: one Crucial x6 and one Crucial x8 and was surprised by the low read speed (48MB/S) when connecting through the USB-A port. The write speed in this case is 417MB/S.
If I use the Thunderbolt 4 port, the read/write speed is closer to the theoretical limits of the SSD (800MB/S), which is expected, as T4 is much faster than USB-A. But why is the read speed when using USB-A this low compared to the write speed?
Yeah, it doesn’t make sense. The read speed should be close to the write speed even when connecting through the USB-A port. The problem is likely on the USB port or the hub you used with this port or the other port if any. So, the USB-A port could be malfunctioning. Or the hub connected to one of the USB-A ports is causing the read speed to drop.
Try the speed test again after directly connecting your SSDs to the USB-A port.
Try a different application to see if the result differs. I used iBoysoft DiskGeeker for Mac to test the read/write speed of my external hard drives before. It’s a good tool.