Either I am asking stupid questions or service here has become less supportive
Neither nor, but your question is just
much too vague for a specific answer. You gave zero information about your hardware setup, your VM setup, the source and the destination disks (SSDs? HDDs?), storage configuration (Raid? ZFS? Topology?) or your network. I can not know how large the file is, how fast the copy process starts and so on. It is not even clear if the destination is a VM on the same PVE or an external device w/o PVE.
On the other hand the
generic effect has been discussed several times. Most times it boils down to buffer bloat: too large buffers, enabled write caches and/or slow destination with consumer SSDs which accept data, fill their internal buffers and need to write it back to the
actual storage area some (5 to 30) seconds later - and block I/O for a surprising long time, leading to a "stuttering" effect.
So the
generic recommendation is to check all physical connections, check Smart-Data and the error log on all disks,
disable write caches for the virtual PVE VM-disks and use Enterprise class SSDs.
Does this help?
