by Alain Raap.
Thanks Ken, I appreciated your help .
Here are some of the links where I found info about NFS configuration and performance:
http://nfs.sourceforge.net/nfs-howto/ar01s05.html
https://www.slashroot.in/how-do-linux-nfs-performance-tuning-and-optimization
https://access.redhat.com/articles/1172303 (needs access login to the Redhat website, useful article)
For our environment it took some time to figure out the best settings for NFS, the backup/restore/import processes were good use cases to test this performance.
For some monitoring commands om Linux we used this article, but there are better monitoring solutions I think:
https://medium.com/netflix-techblog/linux-performance-analysis-in-60-000-milliseconds-accc10403c55