One of the new features introduced in vSphere 5.5 is Flash Read Cache. It allows utilizing the flash memory installed on a host to improve the performance of this host or its virtual machines.
This is achieved by using Virtual Flash File System (VFFS), which is a logical container used by vSphere to group local flash devices into a single resource. VFFS can be used to provide resources to the host and virtual machines simultaneously.
vSphere supports a maximum of 8 flash devices per VFFS, a maximum of 4 TB per flash device, and a maximum of 32 TB in total per VFFS.
As Flash Read Cache is supported by vSphere 5.5 or later, the participating hosts must be running ESXi 5.5, and vCenter should also be Version 5.5 or later.
All participating hosts must have at least one free SSD drive, which will be used as a flash resource.
The virtual flash resource has...