I have a program that at some point uses the mv command to move a pattern matching of files from one folder to another.

mkdir tmpdir
mv /path/to/files/pattern* tmpdir

The folders /path/to/files and tmpdir are both on an NFS share. It is mounted as follows in /etc/fstab:

192.168.10.10:/export/data /mnt/ml nfs auto,actimeo=1 0 0

The NFS share has the following in /etc/exports

/export/data 192.168.0.0/16(rw,nohide,insecure,no_subtree_check,async)

The Problem

Some of these mv commands (as shown earlier) are taking upwards of hours (as indicated by timestamps before and after the move)

Here is a plot of number of files moved vs. the time it took to do so (in minutes).

Any idea as to what could be causing this? Or possible ways to diagnose what is causing this?