The Enhanced Write Filter - Symantec ALTIRIS DEPLOYMENT SOLUTION 6.9 SP4 - V1.0 Manual

Managing Thin Clients
Because application developers can choose from over 10,000 individual feature
components, the image footprint is smaller and can boot basic images as small as 8MB.
The Deployment Agent used for computers running Windows is the same agent that is
installed on thin clients running the Windows XP Embedded operating system. There are
no limitations when installing the Deployment Agent to thin clients from the Deployment
Console. However, you must turn off

The Enhanced Write Filter

on the thin client before
installing the Deployment Agent, so that the agent will be saved to the client's memory.
See also: Installing Deployment Solution agents (page 350)and Deployment agents
(page 109).
The Enhanced Write Filter
The Enhanced Write Filter (EWF) is a unique feature of the Windows XP Embedded
operating system that protects data from being written to the Hard Disk (RAM) storage
area on a thin client. With EWF enabled, any data writes will be redirected to an
alternate storage area called an overlay. The data stored in the overlay gives user's the
appearance that files, programs, or any other data installed to the thin client, will be
permanently saved. However, all data written to the overlay storage area will be deleted
when the thin client reboots. The Enhanced Write Filter is an IT managing feature that
helps control the data stored on a thin client's hard drive.
Some of the tasks Deployment Solution tasks that are impacted by the Enhanced Write
Filter are certain deployment jobs, and installing the Deployment Agent for Windows.
Other tasks such as, creating and distributing images, and modifying the configuration
(computer name or IP address) already have scripts to handle EWF. These jobs disable
EWF first, run other scripts or tasks, and re-enable EWF as the last step of the
deployment job. This ensures that data written to thin clients during the deployment job
will not be lost when clients reboots.
Example: from the Deployment Console in the Jobs pane, located in Samples >
Windows XP Embedded, is a job called Create Disk Image. The script reads as
follow:
Notice that the first line item disables the Enhanced Write Filter, and the second line
item checks to verify that EWF is disabled. The Create Image task creates a copy of the
thin client's image and stores it in the Images folder on the Deployment Share. When
the image task completes, the Enhanced Write Filter is re-enabled, and the thin client
reboots. Because this script handles EWF automatically, thin clients can be managed
from the Deployment Console without concern that data tasks will not be saved to
managed thin clients.
When creating your own Deployment jobs, use the Samples in the Job pane of the
Deployment Console to help you create your own scripts to handle EWF automatically. If
Deployment Solution 258