FFS 6.9 slows down during backup

[eahm]

With USB 3, when a lot of data needs to backup, it goes down to 20-30MBps
from over 150. I don't remember is 6.8 did it too but I think it did, I
will try 6.7 later and I will probably report Monday.

I've tried to copy/paste a big file from Windows before restarting the
external drive or the PC and the speed was around 180MBps, so it must be
FFS.

Any ideas? Thanks.

[eahm]

6.7 and 6.8 same speed. Backing up ~1000 files right now, FFS = ~20-30MBps, stop FFS, copy a large ISO with Windows explorer = ~160-180MBps, restart FFS = ~20-30MBps.

Any ideas?

[Zenju]

USB sticks buffer data first, and write later. So initially it seems as if the USB stick would write at 180 MB/sec while in reality all it does is filling the buffer. You can test this by copying a really large file to the USB stick. At first, you'll see a spike in copy speed, then it evens out at a lower speed, more likely in the 30 MB/s range.

[eahm]

Not a USB stick but SATA Hard Drive on a USB3 Enclosure.

I had to backup less than 200 files with FFS and everything was perfect, ~150-160MBps.

I have no idea why FFS slows down with a lot of files.

[Zenju]

Not a USB stick but SATA Hard Drive on a USB3 Enclosure.

I had to backup less than 200 files with FFS and everything was perfect, ~150-160MBps.

I have no idea why FFS slows down with a lot of files.

External hard disks, just like USB sticks, fill up their internal buffer first and only then start writing actual data.

[eahm]

External hard disks, just like USB sticks, fill up their internal buffer first and only then start writing actual data.

Agree, did few more tests. The thread can be closed, thank you.