In addition to regular storage hard disk drives, ESXi supports Solid State Disks (SSDs).
Unlike the regular hard disks that are electromechanical devices containing moving parts, SSDs use semiconductors as their storage medium and have no moving parts. Typically, SSDs are very resilient and provide faster access to data.
Support of SSDs with ESXi provides the following benefits:
You can use VMFS datastores that are created on SSD storage devices to allocate space for ESXi host cache.
You can use SSDs for such features as Flash Read Cache and Virtual SAN. Local SSDs are required for these features.
Use of SSDs increases virtual machine consolidation ratio as SSDs can provide very high I/O throughput.
Guest operating systems might be able to identify virtual SSD devices.
To detect SSD devices, ESXi uses an inquiry mechanism based on T10 standards. ESXi can automatically detect SSD devices on a number of storage arrays. Check with your vendor whether your storage array supports ESXi SSD device detection.