VMware vSphere ^TM

Simplify virtual machine provisioning and administration with a high performance cluster file system optimized for virtual machines. Central storage of virtual machines with VMFS provides more control, flexibility and performance in managing your virtualized IT environment.

• Deliver high service levels
• Seamlessly manage virtual machine storage
• Deliver high performance and scalability

While conventional file systems allow only one server to have read-write access to the same file system at a given time, VMFS leverages shared storage to allow multiple vSphere hosts to read and write to the same storage concurrently.

• Simplify virtual machine provisioning and administration by efficiently storing the entire virtual machine state in a central location
• Create a point-in-time copy of virtual machine data that can be used for testing, backup and recovery operations
• Support unique virtualization-based capabilities such as live migration of running virtual machines from one physical server to another, automatic restart of a failed virtual machine on a separate physical server and clustering virtual machines across different physical servers
• Add virtual disk space to a running virtual machine to increase available resources or for backup
• Recover virtual machines faster and more reliably in the event of server failure with distributed journaling

Enable multiple VMware vSphere hosts to read and write from the same storage location concurrently.

• Add or delete a vSphere host from a VMFS volume without disrupting other hosts
• Create new virtual machines without relying on a storage administrator
• Grow VMFS volumes on the fly
• Simplify storage management with automatic discovery and mapping of LUNs to a VMFS volume

• Store and access the entire virtual machine state efficiently from a centralized location
• Use large block sizes favored by virtual disk I/O. Uses sub-block allocator for small files and directories
• Connect up to 32 vSphere hosts to a single VMFS volume
• Support single volumes up to 64TB
• Run even the most data intensive production applications such as databases, ERP and CRM in virtual machines
• Benefit from enhanced VMFS performance with volume, device, object and buffer caching

VMFS is included in all VMware vSphere editions and kits.

A virtual machine is stored as a set of files in its own directory in a datastore. Datastores are logical containers, analogous to file systems, which hide specifics of each storage device and provide a uniform model for storing virtual machine files. Datastores can also be used for storing ISO images, virtual machine templates, and floppy images.

Depending on the type of storage you use, datastores can be backed by the following file system formats:

VMFS is a high-performance file system optimized for storing virtual machines. You can deploy a VMFS datastore on any SCSI-based local or networked storage device, including Fibre Channel, Fiber Channel over Ethernet (FCoE) and iSCSI SAN equipment.

NFS is a file system on a NAS storage device. vSphere supports NFS version 3 over TCP/IP. The host can access a designated NFS volume located on an NFS server, mount the volume, and use it for any storage needs.

VMware vSphere Virtual Machine File System (VMFS) is a high-performance cluster file system that provides storage virtualization optimized for virtual machines. VMFS is the default storage management interface for block based disk storage (Local and SAN attached).

VMFS allows multiple instances of VMware vSphere servers to access shared virtual machine storage concurrently. It also enables virtualization-based distributed infrastructure services such as VMware DRS, vSphere HA, vMotion and Storage vMotion to operate across a cluster of vSphere servers. In short, VMFS provides the foundation that enables the scaling of virtualization beyond the boundaries of a single system.

Conventional file systems allow only one server to have read/write access to a specific file at a given time. VMFS leverages shared storage to allow multiple vSphere servers to have concurrent read and write access to the same storage resources. VMFS also has distributed journaling of changes to the VMFS metadata to enable fast and resilient recovery in the event of server crashes or power issues.

VMFS uses on-disk locking to make sure a single virtual machine is not powered up on multiple vSphere hosts at the same time. When vSphere HA is enabled, if a server fails, the on-disk lock for each virtual machine is released under control of vSphere HA, allowing the virtual machine to be restarted on other vSphere hosts.

VMware vSphere 5.0 introduced a new version of vSphere’s virtual machine file system, VMFS-5. VMFS-5 allows greater scalability and performance while reducing complexity. While under the covers many fundamental changes have been made the following enhancements are significant from an operational and architectural aspect:

• 2TB+ Device Support
• Unified block size
• Improved sub-block mechanism
• Additional ATS usage (VAAI Hardware Acceleration for file locking)

VMware vSphere 5.0 allows for a non-disruptive upgrade from VMFS-3 to VMFS-5 ensuring consistency across virtual infrastructures. The unified block size, 1MB, allows for easier deployments and reduced complexity from an architectural and operational aspect while maintaining the scalability and the flexibility that was previously only found with large block sizes. It should be noted that volumes, which are upgraded from VMFS-3 to VMFS-5, would retain their original block size, as modifying the block size would require a reformat of the volume. To allow for greater scalability and to reduce storage overhead associated with small files various enhancements have been made to VMFS-5. These enhancements include optimized sub-block sizes and the allocation of these blocks. These enhancements have resulted in support for large volumes (64TB on a single extent) and higher virtual machine density. The table below depicts the most significant architectural changes for VMFS-5 in comparison to VMFS-3.