Let me try a wild guess, it looks like buffer fragmentation related to
network/ssh/openZFS. The software might desperately try to defragment
many small spaces and that would explain the 100% CPU load during the
low speed transfers. If the defragmentation happens in the kernel, it
also might
The error only occurs on the backup of the large datasets with
incremental updates from say 40 GB to 80 GB. Those datasets are around
250 GB and 450 GB and they contain Virtual Machines. On smaller datasets
I have no issues and in the begin of the transfers, there are no
problems either. The
