FreeFileSync Forum

fix:
reformatted drive from exFAT to NTFS and it works way faster, I'm talking ~x20 times in my case where number of files is in thousands.
apparently some of the performance functions like Trim and garbage collection does not work with exFAT.
however there will be some limitation on NTFS for OS ...

The USB-SATA controller, the SSD controller itself, the NAND architecture, the USB protocol stack overhead on your system, failing storage. Have you actually tried changing any of the hardware involved for testing? What is this "USB-C, top notch SSD" you speak of? Top notch isn't a spec

top ...

FFS has never been the bottleneck in the many years I've been on this forum. Unlikely this will be the first

when I'm mirroring large size files, it maintains good speed. it slows down while transferring small size files. i could not find any issue in task manager or disk performance.
what ...

is this normal behavior of this tool? it takes hours to mirror only a couple of GB data. is robocopy faster comparing with freefilesync?

Doesn't seem out of the ordinary to me. The write cache could be full, or it could just be from a lot of small files. Check Task Manager, should tell you where the bottleneck is. Look for "Active Time" for the drives. The one at 100% is the bottleneck

none of drives are 100%. they are around 2%.

dear Forum members:
I’m experiencing extremely slow sync speeds while running a mirror job ( around 20000 small files to an external SSD). Initially, transfer speed is decent for a few seconds, but over time, it drops drastically—even as low as 15KB/sec.
I have tried adjusting the thread count ...