Windows Embedded 8 Standard for HP Thin Clients - Administrator Guide

3 Unied Write Filter
Unied Write Filter (UWF) is a software tool that protects the contents of and decreases wear on the ash
drive of a thin client by redirecting and caching writes in an overlay, which is a virtual storage space in RAM
that tracks changes to a protected volume (the ash drive). The user experience in Windows is unaected
because the operating system maintains the appearance of writing to the ash drive. When a system restart
occurs, the overlay cache is cleared, and any changes made since the last system startup are lost
permanently. If it is necessary to make permanent system
congurations, an administrator can commit
(persist by writing through to the protected volume) changes stored in the overlay cache prior to a system
restart.
NOTE: The overlay cache is cleared only by a system restart, so users can log out or switch between user
accounts without losing the cached information.
UWF allows you to manage on a per-le basis, so you can immediately (without a system restart) commit les
individually or restore les to their previous state from the underlying volume by discarding the changes. You
can also exclude les from protection so that changes to them are always written directly to the ash drive.
However, you cannot commit the entire UWF overlay cache in a single command.
CAUTION: HP highly recommends proper write lter usage for standard thin client use cases. Proper usage
includes making sure the write lter is enabled during end-user (non-administrator) operation and is disabled
only temporarily by an administrator needing to make changes to the system. The write lter should be re-
enabled as soon as the changes are completed.
HP further recommends never enabling the Windows Page File feature unless the system is congured with a
ash drive that has a capacity suicient for the high volume of writes this feature produces. The use of the
Windows Page File feature with low-capacity ash drives will result in premature wearing of the ash drive,
decreased performance, and a decrease in the lifespan of the thin client.
If your use case requires non-standard write lter usage, please contact HP to ensure that your thin clients
are
congured properly.
4 Chapter 3 Unied Write Filter