VMware VMFS (Virtual Machine File System) is a cluster file system that facilitates storage virtualization for multiple installations of VMware ESX Server, a hypervisor that partitions physical servers into multiple virtual machines. VMFS is part of the virtualization suite called VMware Infrastructure 3.
With VMFS, new virtual machines can be created without the oversight of a storage administrator. The size of a volume can be changed as needed without disrupting network operations. Multiple installations of VMware ESX Server can be used to simultaneously write and read data to and from a single storage location. VMware ESX servers can be added or removed from a VMFS volume without affecting other hosts. The file and block sizes can be adjusted to optimize the I/O (input/output) functionality of each virtual machine. In the event of a server failure, a distributed journaling file system allows for rapid system recovery and prevents catastrophic loss of data.