Remote Virtual machines losing NFS access to NAS mounts

[AusKarlos]

A bit of a long title. But recently within the last month I've had a few Virtual Machines running on a separate server connect to some NAS directories via NFS.
The Virtual Machines all run Ubuntu Server 16.04 and the NAS they connect to is a Qnap TS-1263U-RP (FW 4.3.6.0979) via the 10GBe port to a Managed D-Link switch (With Storm protection disabled as it interferes with some NAS services).
Whats been occurring randomly is all the VMs will lose the ability to read/write to the NFS mounts and not all at the same time. The NFS shares have been setup with IP filters so only those VMs can connect to the shares and the shares have Guest access enabled to make my life easier without adding and users or groups. The NFS shares aren't seen outside the LAN anyway.

There is no indication in the NAS logs of any changes to the NFS shares permissions or otherwise (SSH into the NAS to check file permissions indicate they have not changed), nor are there any logs on the VMs to indicate they have lost connection to the shares. Whats also interesting is that sometimes it will only be a partial loss of access. Like out of the 200 sub-directories 30 of them might be be accessible. The only way to fix it at the moment is to either remount the shares on the VMs or use chmod on the VMs to change all the permissions (which never change to begin with).

Like i said the system that i had setup has been working flawlessly for about 1 year now with no intervention.
Is it possible the amount of Files and Sub-Directories could be causing this issue. As it stands the main share culprit that disconnects the most currently has 6380 directories and ~84000 files.

[constvoid]

Hi - If you look in the Linux & Unix (NFS) sub-forum you will see a number of posts about problems with file permissions on more recent updates of QTS. So far, the only proven solution has been ro roll-back the QNAP to the last reliable version - see those posts for details. Due to the length of time with no solution from QNAP, I have taken more drastic action, and no longer use the QNAP for NFS/SAMBA shares, instead mounting LUNs from the QNAP to one of my VMs via iSCSI, and sharing from there. That way I have complete control over the access permissions, although I dare say performance suffers slightly.