An NFS client built into ESXi uses the Network File System (NFS) protocol over TCP/IP to access a designated NFS volume that is located on a NAS server. The ESXi host can mount the volume and use it for its storage needs. vSphere supports versions 3 and 4.1 of the NFS protocol.
Typically, the NFS volume or directory is created by a storage administrator and is exported from the NFS server. You do not need to format the NFS volume with a local file system, such as VMFS. Instead, you mount the volume directly on the ESXi hosts and use it to store and boot virtual machines in the same way that you use the VMFS datastores.
In addition to storing virtual disks on NFS datastores, you can use NFS as a central repository for ISO images, virtual machine templates, and so on. If you use the datastore for the ISO images, you can connect the CD-ROM device of the virtual machine to an ISO file on the datastore. You then can install a guest operating system from the ISO file.
NFS Protocols and ESXi
ESXi supports NFS protocols version 3 and 4.1. To support both versions, ESXi uses two different NFS clients.
Comparing Versions of NFS Clients
The following table lists capabilities that the NFS version 3 and 4.1 support.
| Characteristics | NFS version 3 | NFS version 4.1 |
|---|---|---|
| Security mechanisms | AUTH_SYS | AUTH_SYS and Kerberos (krb5 and krb5i) |
| Encryption algorithms with Kerberos | N/A | AES256-CTS-HMAC-SHA1-96 and AES128-CTS-HMAC-SHA1-96 |
| Multipathing | Not supported | Supported through the session trunking |
| Locking mechanisms | Propriety client-side locking | Server-side locking |
| Hardware acceleration | Supported | Supported |
| Thick virtual disks | Supported | Supported |
| IPv6 | Supported | Supported for AUTH_SYS and Kerberos |
| ISO images presented as CD-ROMs to virtual machines | Supported | Supported |
| Virtual machine snapshots | Supported | Supported |
| Virtual machines with virtual disks greater than 2 TB | Supported | Supported |
NFS Protocols and vSphere Solutions
The following table lists major vSphere solutions that NFS versions support.
| vSphere Features | NFS version 3 | NFS version 4.1 |
|---|---|---|
| vMotion and Storage vMotion | Yes | Yes |
| High Availability (HA) | Yes | Yes |
| Fault Tolerance (FT) | Yes | Yes |
| Distributed Resource Scheduler (DRS) | Yes | Yes |
| Host Profiles | Yes | Yes |
| Storage DRS | Yes | Initial placement and load balancing based on space utilization. |
| Storage I/O Control | Yes | No |
| Site Recovery Manager | Yes | Site Recovery Manager does not support NFS 4.1 datastores for array-based replication and Virtual Volumes replication. You can use Site Recovery Manager with NFS v 4.1 datastores for vSphere Replication. |
| Virtual Volumes | Yes | Yes |
| vSphere Replication | Yes | Yes |
| VMware Aria Operations | Yes | Yes |
NFS 4.1 and Fault Tolerance
Virtual machines on NFS 4.1 support the new Fault Tolerance mechanism that was introduced in vSphere 6.0. The mechanism can accommodate symmetric multiprocessor (SMP) virtual machines with up to four vCPUs.
NFS 4.1 VMs do not support the legacy Fault Tolerance mechanism.
NFS Upgrades
When you upgrade ESXi from a version earlier than 6.5, existing NFS 4.1 datastores automatically begin supporting functionalities that were not available in the previous ESXi release. These functionalities include Virtual Volumes, hardware acceleration, and so on.
ESXi does not support automatic datastore conversions from NFS version 3 to NFS 4.1.
If you want to upgrade your NFS 3 datastore, the following options are available:
- Create the NFS 4.1 datastore, and then use Storage vMotion to migrate virtual machines from the old datastore to the new one.
- Use conversion methods provided by your NFS storage server. For more information, contact your storage vendor.
- Unmount the NFS 3 datastore, and then mount as NFS 4.1 datastore.
Caution: If you use this option, make sure to unmount the datastore from all hosts that have access to the datastore. The datastore can never be mounted by using both protocols at the same time.
