Configuring VMFS Pointer Block Cache

You can use advanced VMFS parameters to configure the pointer block cache.

As the size of the virtual machine files on the VMFS datastores increases, the number of pointer blocks used by those files also increases. The pointer blocks are used to address file blocks in the large virtual machine files and virtual disks on the VMFS datastore.

You can configure the minimum and maximum sizes of the pointer block cache on each ESXi host. When the size of the pointer block cache approaches the configured maximum size, an eviction mechanism removes some pointer block entries from the cache.

Base the maximum size of the pointer block cache on the working size of all open virtual disk files that reside on VMFS datastores. All VMFS datastores on the host use a single pointer block cache.

The minimum value is based on the minimum guaranteed memory that the system can allocate to the cache. 1 TB of open file space requires approximately 4 MB of memory.

To configure the minimum and maximum values for the pointer block cache, use the Advanced System Settings dialog box of the vSphere Web Client

Table 1. Advanced Parameters to Regulate Pointer Block Cache

Parameter	Values	Description
VMFS3.MaxAddressableSpaceTB	Default value is 32 (in TB).	Maximum size of all open files that VMFS cache supports before eviction starts.
VMFS3.MinAddressableSpaceTB	Default value is 10 (in TB).	Minimum size of all open files that VMFS cache guarantees to support.

You can use the esxcli storage vmfs pbcache command to obtain information about the size of the pointer block cache and other statistics. This information assists you in adjusting minimum and maximum sizes of the pointer block cache, so that you can get maximum performance.