You can create VMFS datastores on Solid State Disks (SSD), and then use these datastores to allocate space for host cache. The host reserves a certain amount of space for swapping to host cache.
The host cache is made up of files on a low-latency disk that ESXi uses as a write back cache for virtual machine swap files. The cache is shared by all virtual machines running on the host. Host-level swapping of virtual machine pages makes the best use of potentially limited SSD space.
Using swap to host cache is not the same as placing regular swap files on SSD-backed datastores. Even if you enable swap to host cache, the host still needs to create regular swap files. However, when you use swap to host cache, the speed of the storage where the host places regular swap files is less important.
The Host Cache Configuration page allows you to view the amount of space on a datastore that a host can use to swap to host cache. Only SSD-backed datastores appear in the list of datastores on the Host Cache Configuration page.
If you have a virtual flash license, you can use virtual flash resource to configure cache on the host. For information, see About VMware vSphere Flash Read Cache.