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14 Dell PS Series Arrays: Advanced Storage Features in VMware vSphere | TR1066
container, and its underlying physical storage, to be used in creating a particular profile. This allowed the
vSphere administrator to create storage profiles that meet their particular business needs.
6.2 Understanding the Virtual Volume storage changes
Traditionally, when deploying storage to a vSphere environment, a volume is created on the array, and this
becomes a datastore within vCenter upon which virtual machines are placed. With Virtual Volumes, some
of this remains the same: Virtual machines are placed within datastores, and all work flows that depend
upon this remain unchanged. What has changed is what is backing the datastore. Backing the datastore is
a new storage object known as a storage container, and while it does contain virtual machines and backs a
datastore, it should not be thought of as a volume. The storage container is more like a reservation of
space on the array. It is from this reservation that virtual machines will consume their storage needs, with
the different Virtual Volumes potentially consuming different performance capabilities and different data-
protection options. With Virtual Volume storage containers, it is possible to have just a single storage
container for the entire environment because the size of a storage container is limited only by the size of
the pool on the PS Series group. However, non-technical issues, such as a preference for keeping virtual
machines separate from different departments or different projects, may drive a preference for multiple
storage containers from a single pool. In an environment with a PS Series group that has multiple pools,
multiple storage containers will be needed because storage containers do not span pools.
Typically, a virtual machine has consisted of a VMX file (configuration file), one or more VMDK files (virtual
disk), a VSWP file (memory swap file), and other miscellaneous files including log files. This changes with
Virtual Volumes, since a virtual machine now consists of a group of volumes on the array consuming
space from the storage container space reservation.
A Virtual-Volume-based virtual machine consists of the following types of virtual volumes:
 Config: A small VMFS-formatted 4Gb volume that hosts the VMX and other miscellaneous files
including log files
 Data: The equivalent of a VMDK, with one existing for each virtual disk attached to the virtual
machine
 Swap: The equivalent of the VSWP file, existing only when the virtual machine is powered on
If a VMware snapshot of the virtual machine is taken, which is now an array-based snapshot, two more
virtual volume types may exist:
 Snapshot: A hidden virtual volume that exists for each data virtual volume included in each virtual
machine snapshot that stores the delta of changes since the previous snapshot was taken
 Memory: A virtual volume that is created if selecting the option to include a memory dump with the
snapshot