vSphere Storage - ESXi 5.1 - Documentation - VMware

n Scalability improvements on storage devices that support hardware acceleration. For information, see
Chapter 21, “Storage Hardware Acceleration,” on page 215.
n Default use of hardware assisted locking, also called atomic test and set (ATS) locking, on storage devices
that support hardware acceleration. For information about how to turn off ATS locking, see “Turn off ATS
Locking,” on page 157.
n Ability to reclaim physical storage space on thin provisioned storage devices. For information, see “Array
Thin Provisioning and VMFS Datastores,” on page 230.
n Online upgrade process that upgrades existing datastores without disrupting hosts or virtual machines
that are currently running. For information, see “Upgrading VMFS Datastores,” on page 165.
For information about block size limitations of a VMFS datastore, see the VMware knowledge base article at
http://kb.vmware.com/kb/1003565.
VMFS Datastores and Storage Disk Formats
Storage devices that your host supports can use either the master boot record (MBR) format or the GUID
partition table (GPT) format.
With ESXi 5.0 and later, if you create a new VMFS5 datastore, the device is formatted with GPT. The GPT
format enables you to create datastores larger than 2TB and up to 64TB for a single extent.
VMFS3 datastores continue to use the MBR format for their storage devices. Consider the following items when
you work with VMFS3 datastores:
n For VMFS3 datastores, the 2TB limit still applies, even when the storage device has a capacity of more
than 2TB. To be able to use the entire storage space, upgrade a VMFS3 datastore to VMFS5. Conversion
of the MBR format to GPT happens only after you expand the datastore to a size larger than 2TB.
n When you upgrade a VMFS3 datastore to VMFS5, the datastore uses the MBR format. Conversion to GPT
happens only after you expand the datastore to a size larger than 2TB.
n When you upgrade a VMFS3 datastore, remove from the storage device any partitions that ESXi does not
recognize, for example, partitions that use the EXT2 or EXT3 formats. Otherwise, the host cannot format
the device with GPT and the upgrade fails.
n You cannot expand a VMFS3 datastore on devices that have the GPT partition format.
VMFS Datastores as Repositories
ESXi can format SCSI-based storage devices as VMFS datastores. VMFS datastores primarily serve as
repositories for virtual machines.
With VMFS5, you can have up to 256 VMFS datastores per host, with the maximum size of 64TB. The required
minimum size for a VMFS datastore is 1.3GB, however, the recommended minimum size is 2GB.
NOTE Always have only one VMFS datastore for each LUN.
Chapter 17 Working with Datastores
You can store multiple virtual machines on the same VMFS datastore. Each virtual machine, encapsulated in
a set of files, occupies a separate single directory. For the operating system inside the virtual machine, VMFS
preserves the internal file system semantics, which ensures correct application behavior and data integrity for
applications running in virtual machines.
When you run multiple virtual machines, VMFS provides specific locking mechanisms for virtual machine
files, so that virtual machines can operate safely in a SAN environment where multiple ESXi hosts share the
same VMFS datastore.
In addition to virtual machines, the VMFS datastores can store other files, such as virtual machine templates
and ISO images.
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