Very slow operation with 512GB key

[Boris1]

I use a 256GB USB key to synchronize my various Windows 10 (v1709) computers.
Recently, I changed to a 512GB key but this key is unusable with ffs because of slow operation.
Both keys are quite good (256GB Sandisk Ultra and 512GB Corsair Flash Voyager Super X2).
Here are the puzzling numbers:
Both keys contain exactly the same data (60,000 files). I just added a 546MB file to the source so that only this file is synchronized and ffs does only 2 operations: Creating lock files, Copying 546MB file.
With 512GB key: Creating lock files took 36 seconds; Copying 546MB file took 10 minutes. Copying manually the 546MB file to the same location took ~4 seconds.
With 256GB key: Creating lock files took <1 second; Copying 546MB file took 50 seconds. Copying manually the 546MB file to the same location took ~8 seconds.
This test was done on the same computer (with disablelastaccess =1, same antivirus). Keys have identical NTSF configuration. ffs configuration is default. ffs version is 10.17. (The behavior was reproduced on 3 different computers).
I should mention that I actually bought 3 512GB Corsair Flash Voyager Super X2 keys and tested all 3.
I understand that keys might not have the same performance. What escapes me is why ffs copy can take 10 minutes while a simple copy/paste takes 4 seconds. Thsi is a mystery to me, especially for such a really great software.
I would appreciate any suggestion. Thanks.

[officeboy]

Take a look at my earlier posts on 'FFS performance and 'disablelastaccess' setting in Windows 10' and see if it applies to your issue.

[Boris1]

I did look at your posts. In my case, setting disablelastaccess =1 did not make a noticeable difference.
As I said in my message, all my tests were conducted with disablelastaccess =1. In any case, tests were conducted with only one somewhat big file to synchronize. I would not expect disablelastaccess to impact teh results in that case.

[Zenju]

Does it make a difference when you disable folder locks? (LockDirectoriesDuringSync: https://freefilesync.org/manual.php?topic=expert-settings)

[Boris1]

I tried that too. Didn't seem to change anything, besides avoiding the creation of lock files.

[xCSxXenon]

Take a look at my earlier posts on 'FFS performance and 'disablelastaccess' setting in Windows 10' and see if it applies to your issue.

Please stop spamming this on every thread with slow operation. That seems to have worked for you and maybe one other person, it's not the "end all be all" answer to slow speeds. You're not even linking the post either, just making people trudge through post history to find it.