5.2

Reclaim Disk Space on Linked-Clone Desktops
In
vSphere 5.1 and later, you can configure the disk space reclamation feature for linked-clone desktop pools.
Starting in vSphere 5.1, View creates linked-clone virtual machines in an efficient disk format that allows ESXi
hosts to reclaim unused disk space on the linked clones, reducing the total storage space required for linked
clones.
As users interact with linked-clone desktops, the clones' OS disks grow and can eventually use almost as much
disk space as full-clone desktops. Disk space reclamation reduces the size of the OS disks without requiring
you to refresh or recompose the linked clones. Space can be reclaimed while the virtual machines are powered
on and users are interacting with their desktops.
In View Administrator, you cannot directly initiate disk space reclamation for a pool. You determine when
View initiates disk space reclamation by specifying the minimum amount of unused disk space that must
accumulate on a linked-clone OS disk to trigger the operation. When the unused disk space exceeds the
specified threshold, View directs the ESXi host to reclaim space on that OS disk. View applies the threshold to
each virtual machine in the pool.
You can use the vdmadmin -M option to initiate disk space reclamation on a particular virtual machine for
demonstration or troubleshooting purposes. See “Reclaiming Disk Space on Virtual Machines Using the -M
Option,” on page 420.
You can configure disk space reclamation on linked clones when you create a new pool or edit an existing pool.
For an existing pool, see "Upgrade Desktop Pools for Space Reclamation" in the VMware Horizon View
Upgrades document.
If a View Composer is refreshing, recomposing, or rebalancing linked clones, disk space reclamation does not
take place on those linked clones.
Disk space reclamation operates only on OS disks in linked clones. The feature does not affect View Composer
persistent disks and does not operate on full-clone virtual machines.
Native NFS snapshot technology (VAAI) is not supported in pools that contain virtual machines with space-
efficient disks.
Prerequisites
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Verify that your vCenter Server and ESXi hosts are version 5.1 with ESXi 5.1 download patch
ESXi510-201212001 or later.
In an ESXi cluster, verify that all the hosts are version 5.1 with download patch ESXi510-201212001 or later.
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Verify that VMware Tools that are provided with vSphere version 5.1 or later are installed on all the linked-
clone virtual machines in the pool.
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Verify that all the linked-clone virtual machines in the pool are virtual hardware version 9 or later.
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Verify that the virtual machines use SCSI controllers. Disk space reclamation is not supported on virtual
machines with IDE controllers.
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Verify that the linked-clone desktops run Windows XP or Windows 7. Disk space reclamation is not
supported on Windows 8 desktops.
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Verify that disk space reclamation is enabled in vCenter Server. This option ensures that the virtual
machines in the pool are created in the efficient disk format that is required to reclaim disk space. See
“Allow vSphere to Reclaim Disk Space in Linked-Clone Virtual Machines,” on page 19.
Chapter 5 Creating Desktop Pools
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