Datasheet

CHAPTER 1 VMware VSphere 4 OVerView

vStorage VMFS Volume Grow The VMFS Volume Grow capability in vSphere allows

you to dynamically expand the size of an existing data store that resides on a VMFS volume

without disrupting running virtual machines. It complements the dynamic LUN expansion

capability that exists in many storage array offerings today. After you expand the LUN where

a data store resides through an array management utility, you can use VMFS Volume Grow to

expand the VMFS extent on the expanded LUN. You can verify the increased VMFS volume

(data store) size from vCenter Server.

For earlier versions of ESX, you have to use VMFS spanning across multiple LUNs to increase

the size of an existing VMFS volume. First, you expand the LUN upon which the VMFS vol-

ume resides; next, you create a separate disk partition in that additional storage space and

add the new partition as if you were adding a second LUN to the VMFS volume.

Hot extend for virtual disks Hot extend for virtual disks allows you to add virtual stor-

age to running virtual machines without any downtime. You can use hot extend for VMFS

ﬂat virtual disks using persistent mode and for ones that do not have any VMFS snapshots.

You will need to run guest operating system tools for it to start using the additional storage.

Together with the VMFS Volume Grow capability, this feature provides a very ﬂexible and

dynamic way to manage storage capacity growth.

Vi r t u a l di S k th i n Pr o V i S i o n i n g

VMware virtual disk thin provisioning enables over-commitment of storage capacity similar to

CPU and RAM over-commitment. It allows the storage administrator to conﬁgure more virtual

machine storage capacity than the actual physical storage currently available. This is possible

because thin provisioning enables virtual machines to utilize storage space on an as-needed basis.

When a virtual disk is initially allocated, it is assigned 1 MB of storage space in the data store. As

that disk space is used up, additional 1 MB chunks of storage are allocated for the virtual disk

so that the underlying storage demand will grow as its size increases. This dynamic allocation

reduces storage over-provisioning and increases storage utilization, allowing you to defer stor-

age purchases until they are really required. This can signiﬁcantly reduce an organization’s

storage budget.

VMware’s desktop products such as VMware Workstation have long provided the feature

to allow virtual machines to allocate storage space as needed. In Virtual Infrastructure 3, thin

provisioning was used by default for virtual disks created on NFS data stores and was available

for block-based data stores through the command line. With VMware vSphere, vCenter now

fully supports virtual disk thin provisioning for all virtual disks when deploying or migrating

virtual machines (Figure 1.8).

vCenter Server 4.0 continuously monitors the storage allocations and tracks it against storage

capacity so that it can generate alerts and alarms to warn vSphere administrators against any

future “out of space” situations.

Virtual disk thin provisioning should not be confused with the same thin provisioning

NOTE

that an array vendor might offer. In fact, with vSphere, you now have the capability of doing thin

provisioning at the data store level in addition to doing thin provisioning at the storage array.

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