VMware VMFS

Infobox Software
name = VMware VMFS
logo =


caption =
developer = VMware, Inc.
latest_release_version = 3
latest_release_date = June 2006
genre = Clustered file system
license = Proprietary
website = [http://www.vmware.com/products/vi/esx/vmfs.html www.vmware.com]

VMware VMFS (Virtual Machine File System) is VMware, Inc.'s cluster file system. It is used by VMware ESX Server and the company's flagship server virtualization suite, VMware Infrastructure.cite web |url=http://www.vmware.com/products/vi/esx/vmfs.html |title=Deliver High-performance Storage for Virtual Machines |accessdate=2007-09-26 |publisher=VMware] It was developed and is used to store virtual machine disk images, including snapshots. Multiple servers can read/write the same filesystem simultaneously, while individual virtual machine files are locked. VMFS volumes can be logically "grown" (non-destructively increased in size) by spanning multiple VMFS volumes together.

Version history

There are three versions of VMFS, corresponding with ESX Server product releases.

* VMFS version 1 was used by ESX Server v1.x, which is not sold anymore. It didn't feature the cluster filesystem properties and was used only by a single server at a time. VMFS1 is a flat filesystem with no directory structure. -- Officially named "VMware File System"
* VMFS version 2 is used by ESX Server v2.x and (in a limited capacity) v3.x. While ESX Server 3.x can read from VMFS2 volumes, it will not mount them for writing. VMFS2 is a flat filesystem with no directory structure. -- Officially named "VMware File System"
* VMFS version 3 is used by ESX Server v3.x. As a most noticeable feature, it introduced directory structure in the filesystem. Older versions of ESX Server cannot read or write VMFS3 volumes. Beginning from ESX 3 and VMFS3, virtual machine configuration files are stored in the VMFS partition by default. -- Officially named "VMware Virtual Machine File System"

Features

* Allows access by multiple ESX Servers at the same time by implementing per-file locking. SCSI Reservations are only implemented when LUN meta data is updated (e.g. file name change, file size change, etc.)
* Add or delete an ESX Server from a VMware VMFS volume without disrupting other ESX Server hosts.
* LVM allows for adaptive block sizing and addressing for growing files allows you to increase a VMFS volume on the fly (only by spanning multiple VMFS volumes; extending a volume by growing a LUN is not supported)
* Optimize your virtual machine I/O with adjustable volume, disk, file and block sizes.
* Recover virtual machines faster and more reliably in the event of server failure with Distributed journaling.

Limitations

* Can be shared with up to 32 ESX Servers.cite web |url=http://www.vmware.com/pdf/vi3_301_201_config_max.pdf |title=Configuration Maximums for VMware Infrastructure 3 |format=PDF |date=2007-07-23 |accessdate=2007-09-26 |publisher=VMware]
* Can support LUNs with max size of 2TB.cite web |url=http://www.vmware.com/pdf/vi3_301_201_config_max.pdf |title=Configuration Maximums for VMware Infrastructure 3 |format=PDF |date=2007-07-23 |accessdate=2007-09-26 |publisher=VMware]

See also

* List of VMware software

References

External links

* [http://www.vmware.com/pdf/vmfs-best-practices-wp.pdf VMFS Technical Overview and Best Practices] - VMware, Inc.
* [http://www.vmware.com/products/vi/esx/vmfs.html VMware VMFS product page] - VMware, Inc.
* [http://www.vifaq.com/index.php?option=com_content&task=view&id=25&Itemid=2 VMware over NFS - Why?] - vifaq.com