Unfortunately, this will cause NFS session/connection reset, as explained in the following NAS LV expanding procedure:
Resizing NAS LV in NFS cluster will cause shares residing on the LV in question to be inaccessible for ~1-4s. Thus, we do recommend modifying NAS LV size during maintanance window / planned downtime.
Please note that the procedure itself requires:
1. moving all resources to one node
2. enabling "maintanance mode"
3. stopping the cluster with Virtual IPs enabled
4. stopping all replication tasks
5. removing NFS tasks from resources manager / pool
6. removing all replication tasks
7. disabling replication on an LV in question [Volume Manager > Modify LV > uncheck "use replication"]: this part will cause interruption in access to NFS share
8. resizing NAS LV
9. re-enabling replication on a NAS LV - this part will cause interruption in access to NFS share
10. creating new replication tasks
11. launching replication tasks
12. adding NFS tasks to resource mnager / pool
13. running the cluster
Also, depending if you already have a free space on a VG, or need to extend RAID VD, you would only need to follow the procedure above for former case, and also execute "PVRESIZE" via DSS CLI in latter case.