Virtual Disk API Programming Guide - Documentation - VMware

Glossary
D differential backup
Saving system data changed since the last full backup, so only two restore steps are necessary.
E extent
In the context of VMDK, a split portion of virtual disk, usually 2GB.
F flat
Space in a VMDK is fully allocated at creation time (pre‐allocated). Contrast with sparse.
H hosted disk
A virtual disk stored on a hosted product, such as VMware Workstation, for its guest operating system.
I incremental backup
Saving system data changed since the last backup of any type.
M managed disk
A virtual disk managed by an ESX/ESXi host or VMware vCenter, contained within a VMFS volume.
monolithic
The virtual disk is a single VMDK file, rather than a collection of 2GB extents. Contrast with split.
N NBD
Network block device, a VMware method for over‐the‐network access.
P proxy
A physical or virtual machine running an operating system with third‐party backup software. The proxy
is used to perform file‐level and image‐level virtual machine backups.
Q quiescing
A method of bringing the on‐disk data of a physical or virtual computer into a state suitable for backups.
Quiescing may include flushing disk buffers from the operating system’s in‐memory cache or other tasks.
R RDM (Raw Device Mapping)
Enables a virtual machine to directly access a LUN on the physical storage subsystem (SAN connected by
Fibre Channel, iSCSI, or SAS). At the same time, the virtual machine has access to the disk that is using a
mapping file in the VMFS name space. Performance is similar to VMDK.
S sparse
Space in a VMDK is allocated only when needed to store data. Contrast with flat.
split
The virtual disk is a collection of VMDK files containing 2GB extents. Contrast with monolithic.
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