Virtual machines residing on NFS storage become unresponsive during a snapshot removal operation

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

When using NFSv3 to mount NFS datastores, and a VADP-enabled backup solution that uses the hot-add method, you experience these symptoms:

• During a snapshot creation or removal operation, virtual machines residing on NFS storage become unresponsive, it is also observed ESXi host also going unresponsive at the same time.
• When removing snapshots after backing up a virtual machine residing on an NFS datastore using a backup application, the virtual machine becomes unresponsive for approximately 30 seconds.
• Removing snapshots after backing up a virtual machine residing on an NFS datastore takes a long time to complete.
• This issue occurs when the target virtual machine disk was hot-added for the backup/restore operation.

Environment

VMware vSphere ESXi 6.5
VMware vSphere ESXi 8.0
VMware vSphere ESXi 7.0
VMware vSphere ESXi 6.7

Cause

This issue occurs when the target virtual machine and the backup appliance reside on two different hosts, and the NFSv3 protocol is used to mount NFS datastores. A limitation in the NFSv3 locking method causes a lock timeout, which pauses the virtual machine being backed up.

Resolution

This issue is resolved by using the NFSv4 protocol for mounting NFS volumes.

Note: NFSv4 is released with ESXi 6.0, and later . It is not available in earlier versions.

To work around this issue, ensure that the virtual machine resides in the same host where the backup appliance is installed.

Note: Alternatively, you can use LAN/NBD transport that uses the NFC (Network File Copy) in your backup solution or disable SCSI hot-add through the backup software. For more information about NBD transport, see the Virtual Disk Transport Methods section in the Virtual Disk Programming guide.

Additional Information

For more information on virtual machine losing connection during snapshot removal, see VM Loses Connection During Snapshot Removal.