Windows Embedded Standard 7 for HP Thin Clients - Administrator Guide

2 Write filters
A write filter provides a secure environment and can extend the life of a thin client by protecting it
from unauthorized and excessive writes to the flash drive. Write data is intercepted by a write filter
and cached in the RAM drive, and as a result, lost after the next thin client restart. There are two
different write filters available:
●
Enhanced Write Filter (EWF)—Protects an entire volume (C: by default) by caching all write data
into an overlay
●
File-Based Write Filter (FBWF)—Caches individual files, allowing you to specify files or folders to
be excluding from protection (excluded files will always write to the underlying volume)
NOTE: EWF is enabled by default. Only one write filter can be used at a time.
For an overview of the different ways to manage the write filters, see Write filter management
overview on page 3.
For information about how to make permanent changes to the system, see
Configuring the write
filters to allow permanent changes on page 6.
For information about how to cancel a write filter action previously assigned to take place on the next
thin client restart, see
Clearing the boot command on page 8.
CAUTION: Ensure that the write filter is enabled after committing necessary configurations to the
thin client flash drive. During normal operation of the thin client, the write filter must be enabled. Also
ensure that Page File is not enabled on thin clients with flash memory storage. Failure to follow these
required actions can void the warranty of the flash storage device. In the event of damage to the flash
storage device due to operation with a disabled write filter or enabled Page File, the damage will not
be covered by HP warranty.
Write filter management overview
There are three different ways of managing the write filters:
●
Status icon
●
HP Write Filter Configuration utility
●
Command line
Write filter management overview 3