Definition of the advanced NFS options

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides information on advanced NFS settings.

Warning: It's not recommended to make any changes with default settings if there was no issues with the system.

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Resolution

To access the NFS advanced options:

1. Log in to the VMware vSphere Client.
2. Select the ESXi host.
3. Click the Configuration tab.
4. Click Advanced Settings.
5. Select NFS.

List of each setting with a brief description:

Note: If the NFS HeartBeat advanced option values are modified, you must reboot the ESXi host.

• NFS.DiskFileLockUpdateFreq
  
  The time between updates to the NFS lock file on the NFS server. Increasing this value increases the time it takes to recover stale NFS locks. For more information, see NFS Locking.
   
• NFS.HeartbeatFrequency
  
  This sets how often the NFS heartbeat world runs to see if any NFS volumes need a heartbeat request. For more information, see NFS Heartbeats.
   
• NFS.HeartbeatTimeout
  
  The amount of time before stoping a heartbeat request. For more information, see NFS Heartbeats.
   
• NFS.HeartbeatDelta
  
  The amount of time after a successful GETATTR request before the heartbeat world issues a heartbeat request for a volume. If an NFS volume is in an unavailable state, an update is sent every time the heartbeat world runs (NFS.HeartbeatFrequency seconds). For more information, see NFS Heartbeats.
   
• NFS.HeartbeatMaxFailures
  
  The number of consecutive heartbeat requests that must fail before the server is marked as unavailable. For more information, see NFS Heartbeats.

 

• NFS.LockRenewMaxFailureNumber
  
  The number of lock update failures that must occur before the lock is marked as stale. For more information, see NFS Locking.
   
• NFS.LockUpdateTimeout
  
  The amount of time before a lock update request is stopped. For more information, see NFS Locking.
   
• SunRPC.MaxConnPerIP
  
  This option defines the maximum number of TCP/IP connection per NFS Server.
   
• NFS.MaxVolumes
  
  The maximum number of NFS volumes that can be mounted. The TCP/IP heap might be required to increase to accommodate the number of NFS volumes configured. Refer KB Increasing the default value that defines the maximum number of NFS mounts on an ESXi/ESX host

 

• NFS.ReceiveBufferSize
  
  This is the size of the receive buffer for NFS sockets. This value is chosen based on internal performance testing. VMware does not recommend adjusting this value.
   
• NFS.SendBufferSize
  
  The size of the send buffer for NFS sockets. This value is chosen based on internal performance testing. VMware does not recommend adjusting this value.
   
• NFS.SyncRetries
  
  The number of retries before synchronous IO fails (10 seconds per retry).
• NFS.VolumeRemountFrequency
  
  This determines how often an NFS volume attempts to mount when it is initially unable to mount. After a volume is mounted it never needs to be remounted. The volume is marked unavailable if it loses connectivity to the NFS server but it still remains mounted.
  
  Note: Some of these advanced options might be missing or additional options added depending on the version of ESXi host.

NFS Locking

NFS locking on ESXi does not use the NLM protocol. VMware has its own locking protocol. NFS locks are implemented by creating lock files on the NFS server. Lock files are named.lck-fileid, where fileid is the value of the fileid field returned from a GETATTR request for the file being locked.

When a lock file is created, an update is periodically (everyNFS.DiskFileLockUpdateFreqseconds) sent to the lock file to let other ESX hosts know that the lock is still active. The lock file updates generate small (84 byte) WRITE requests to the NFS server. Changing any of the NFS locking parameters changes how long it takes to recover stale locks. This formula can be used to calculate how long it takes to recover a stale NFS lock:

(NFS.DiskFileLockUpdateFreq * NFS.LockRenewMaxFailureNumber) + NFS.LockUpdateTimeout

If any of these parameters are modified, it is very important that all ESX hosts in the cluster use identical settings. Having inconsistent NFS lock settings across ESX hosts can result in data corruption.

            Note: Locking types can differ in versions of NFS see NFS protocols
 

NFS Heartbeats

NFS heartbeats are used to determine whether or not an NFS volume is still available. NFS heartbeats are actually GETATTR requests on the root file handle of the NFS Volume. There is a system world that runs everyNFS.HeartbeatFrequencyseconds to check if it needs to issue heartbeat requests for any of the NFS volumes. If a volume is marked available, it only issues a heartbeat if it has been NFS.HeartBeatDelta seconds since it issued a successful request (for example, a successful GETATTR, READ, READDIR, etc) that does not modify the attribute for that volume. The NFS heartbeat world always issues heartbeats for NFS volumes which are marked unavailable.

 

Use this formula to calculate the Minimum and the Maximum time for an ESXi to mark an NFS volume as unavailable:

Minimum time to mark a volume down(minTime) = (HeartbeatFrequency * (HeartbeatMaxFailures - 1)) + HeartbeatTimeout

Maximum time to mark a volume down(maxTime) = HeartbeatDelta + HeartbeatFrequency + minTime

Default values for these variables in ESXi 7.x/8.x:

• HeartbeatFrequency  12
• HeartbeatTimeout 5
• HeartbeatDelta 5
• HeartbeatMaxFailures 10