Inconsistent speed when copying files from NFS share

I have mounted a folder from my Synology NAS using NFS and when copying a large file I get inconsistent speeds in the file manager. Initially, the estimate is way higher than the maximum expected on a 1Gbit/s LAN and over time the speed estimate goes down slowly.

Example, the estimated transfer speed starts with over 1 Gb/s and the progress bar indicates that most of the file is copied in just a couple of seconds. Then the progress bar hangs on 100%. After a while, the file copy finishes successfully and the speed estimate is a more expected 80 MB/s at the end.

Is there anything that can be done to improve this? Tested with same result in KDE/Dolphin and Cinnamon/Nemo.

Is the file fragmented? Is there other network traffic? Is there other concurrent file access on the NAS? Is the file spread between inner and outer regions of a disk platter? Are you transferring data faster than read buffers can keep up?

There are many, many (many) possible reasons for this.

You can’t trust progress bars. Ever. They are simply present as an indication that “something” is happening at some point between “start” and “end”.

They are also incredibly unreliable from a UX perspective:

image

More discussion:

Also:

2 Likes

Thanks @jonathon, the network is not utilized by anything else (1 Gbit LAN) and the NAS should be able to deliver way more speed than the network can deliver. I remember from the dark times when I used Windows, a file copy to or from the NAS displayed exact speed results and progress bar (but I did not use NFS at that time, instead the “mount folder” in Windows, cannot remember the exact technical term).

Anyway, I believe the network and NAS was OK at that time and nothing has been changed in the network since…