Slow Transfers (Consistent Across Many Versions)

[TheoreticalPlacement]

First, I want to say I really like FreeFileSync and use it weekly. It's been the best backup software I've tried, and I've tried a lot.

However, I have a persistent issue with slow transfers which has been affecting me since I first started using FFS several versions ago. I'm running Windows 10 and have a few different backup hard drives, all of which can easily maintain 100-130 MB/s writes over USB 3.0 - but only when copying files via Windows Explorer or another transfer program. FreeFileSync is -sometimes- significantly slower. I understand that lots of little files are slow to transfer, especially when transferring to a hard drive, but I'm talking about the sustained transfer speed of large files (such as .mp4 and .mov files). The same file transferred manually through Windows Explorer at 120 MB/s will only transfer at maybe 37 MB/s when backing up through FreeFileSync.

To get full transfer speeds in previous versions, it variously required restarting FFS, reinstalling FFS, unplugging and re-plugging the external drive, or restarting the PC. However, with the latest version 11.14, it is 100% consistent in transferring files about 4x slower than it should. Nothing I do changes the transfer speed; it is always pegged at around 37 MB/s, and of course significantly slower when transferring lots of small files. These files are all locally stored on the PC, the processor is a Ryzen 5 3600, I'm running 16GB of RAM, and these files are being backed up from a Crucial P1 1TB NVMe SSD with sustained read speeds of 2 GB/s. And again, files transferred through Windows Explorer and all other backup software I've used are copied/backed up at the full speed of whatever external backup drive is plugged in - this is an issue with FreeFileSync itself.

Does anyone know what could be causing this? Maybe a setting inside FFS?

[xCSxXenon]

viewtopic.php?t=8839
viewtopic.php?t=8855

Kind of an open-end issue at the moment. Although for other users here, please make sure you search the forum before posting to cut down on duplicates and keep information consolidated.

[mb6391]

Just throwing this one out - may be of assistance. Have you tried adjusting the Performance improvements in the comparison tab.

From FFS help - https://freefilesync.org/manual.php?topic=performance

Also from experience, I had a problem a while ago that whilst an external drive was advertised as USB3 it was in fact USB2.

Anyway, good luck but sounds like a bit of (more) frustrating trial and error.

[xCSxXenon]

That setting doesn't help you with local transfers. It only helps when transfers are artificially limited, not when they are simply maxed out

[Zenju]

From other reports it seems FFS 11.14 isn't treated so favourably by Microsoft's virus scanner. I have a hunch, this slowdown could be AV-related.
As always, you can check disk activity and find interferring processes via Process Monitor: https://freefilesync.org/faq.php#trace