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NFS datastores leverage the Dell Unity File System, a 64-bit file system architecture, which includes several advantages. Initial Dell Unity OE versions offered a 64 TB maximum file system size, which was increased to a maximum potential capacity of 256 TB with Dell Unity OE version 4.2. Other features include file system shrink, replication, snapshots, increased limits, and more. For more information about Dell Unity File System, see the Dell Unity: NAS Capabilities white paper on the Dell Unity XT Info Hub.
NFS datastores require an NFS-enabled NAS server to be created first. In the NFS datastore creation wizard, access can be configured to ESXi hosts. For any ESXi hosts that are provided access to this datastore, the new storage is automatically rescanned and made available to the ESXi host. The wizard also allows the Host IO Size to be selected, as shown in Figure 4.
The Host IO Size specifies the smallest guaranteed physical mapping within the file system. Select 8K (default), 16K, 32K, 64K, or a specific application from the drop-down menu to change this mapping. Matching this to the application’s block size provides benefits such as eliminating the overhead and performance impact of unnecessarily granular mappings.
If you are unsure about this setting, or if the datastore is for general-purpose use, use the default of 8K because this setting cannot be changed after the datastore is created. Configuring this to be larger than the actual host I/O size could result in increased overhead, reduced performance, and higher flash wear. However, configuring this to be too small does not allow the datastore to fully take advantage of the performance optimizations when the I/O size is matched. It is recommended to leave this at the default value of 8K for general-purpose datastores, or if you are not certain which application or I/O size is used on this datastore. If the system detects that most of the I/Os are different than the configured file system size, a warning is generated in Unisphere to alert the administrator.