Question Write speed issues - Sandisk Extreme Pro USB

Jun 24, 2022
Had a 512Gb pen drive for a year or so and enjoyed write speeds around the 200Mb/s. Upgraded to a 1Tb model today and write speeds on the new drive are down to around 70-100Mb/s ?. Initially write speed is around the expected 400Mb/s but quickly drops after around 3 seconds or so. I tried transferring a file to my old 512Gb and that's dropped to around 100Mb/s too ??. Source file on a very fast M2 drive (around 5Gb/s) so no problem there. Same speed drop if copying from old to new USB key.

Both keys formatted NTFS 4096 byte allocation (ExFAT 256Kb allocation makes no difference)

USB3 'SS-10' port. Both drives policy 'quick removal' ('better performance' only gives a short boost before again dropping speed). PC restarted, no improvement at all.

What's the game here ?
If nothing else changed, I'd say start with a CrystalDiskMark run, but using a 8GB test size instead of 1GB and see what the sequential transfer results are. Also try transferring a file that's between 100-300MB.

If the CrystalDiskMark results are what you seeing, but the smaller file transfer is faster, then you're hitting the caching limits of the thumb drive.