ESXi supports five different storage technologies as of version 5.5

1. DAS ( Direct attached storage) or Local storage
2. ISCSI( Internet small computer system interface)
3. FC (Fiber channel)
4. FcoE ( Fiber channel over ethernet)
5. NAS ( Network attached storage)


There are two type of datastore:
1. VMFS Based
2. NFS Bsed

Datastores are a place where you can place your virtual machine files, iso images and VM templates.
- VMFS datastores are backed by either disks or Luns which are block level.
- A folder you create, publish over network and mount it on ESXi is called
NFS ( Network file system), which is file level storage.

Diff:

1. VMFS :
Creating VMFS DataStore : First connectivity is made from ESX host to storage by using FC or iSCSI or FCoE protocols.
 Once connectivity is established to the storage array, we can use the vSphere Web Client to browse the available LUNs,
 and to create a VMFS-formated Datastore. And now, we have space that's suitable to store our virtual machines.
 So this file system is created by the ESXi Host i.e. VMFS. Support many vSphere features,
 like high availability, vMotion and DRS.


2. NFS :

Creating NFS DataStore : Here ESX host make connectivity using standard TCP network protocol to NFS device(NAS device),
NFS device owns and operates file system. NFS device share folder(NFS file system) to EXS host and ESX host creates NFS
datastore on that folder means storage and file system is in control of NFS device.
NFS also supports features like high availability, vMotion and DRS.
There are two key features that are not supported, and those are Raw Device Mappings and Boot from SAN.