6.0.2

Overview of Windows 7 and Windows 8 Services and Tasks That Cause Linked-
Clone Growth
Certain services and tasks in Windows 7 and Windows 8 can cause linked-clone OS disks to grow
incrementally every few hours, even when the linked-clone machines are idle. If you disable these services
and tasks, you can control the OS disk growth.
Services that affect OS disk growth also generate IOPS on Windows 7 and Windows 8 virtual machines. You
can evaluate the benefits of disabling these services on full virtual machines as well as linked clones.
Before you disable the Windows 7 or Windows 8 services that are shown in Table 3-9, verify that you took
the optimization steps in “Optimize Guest Operating System Performance for All Windows Versions,” on
page 36 and “Optimize Windows 7 and Windows 8 Guest Operating System Performance,” on page 37.
Table 3‑9. Impact of Windows 7 and Windows 8 Services and Tasks on OS Disk Growth and IOPS When OS Is Left
Idle
Service or Task Description
Default
Occurrence or
Startup
Impact on
Linked-Clone OS
Disks Impact on IOPS
Turn Off This
Service or Task?
Windows
Hibernation
Provides a power-
saving state by
storing open
documents and
programs in a file
before the
computer is
powered off. The
file is reloaded
into memory when
the computer is
restarted, restoring
the state when the
hibernation was
invoked.
Default power-
plan settings
disable
hibernation.
High.
By default, the size
of the hibernation
file,
hiberfil.sys, is
the same as the
installed RAM on
the virtual
machine. This
feature affects all
guest operating
systems.
High.
When hibernation
is triggered, the
system writes a
hiberfil.sys file
the size of the
installed RAM.
Yes
Hibernation
provides no benefit
in a virtual
environment.
For instructions, see
“Disable Windows
Hibernation in the
Parent Virtual
Machine,” on
page 48..
Windows
Scheduled Disk
Defragmentation
Disk
defragmentation is
scheduled as a
background
process.
Once a week High.
Repeated
defragmentation
operations can
increase the size of
linked-clone OS
disks by several
GB and do little to
make disk access
more efficient on
linked clones.
High Yes
Windows Update
Service
Detects,
downloads, and
installs updates for
Windows and
other programs.
Automatic startup Medium to high.
Causes frequent
writes to the
linked-clones' OS
disks because
update checks
occur often. The
impact depends on
the updates that
are downloaded.
Medium to high Yes, if you use View
Composer
recompose to install
Windows updates
and refresh to
return OS disks to
their original
snapshots.
Chapter 3 Creating and Preparing Virtual Machines
VMware, Inc. 39