Windows 10 IoT Enterprise - Administrator Guide
A Unied Write Filter
IMPORTANT: If your thin client has HP Write Manager, see the administrator guide for HP Write Manager for
instructions. This appendix applies only to thin clients that do not have HP Write Manager.
Unied Write Filter (UWF) is an operating system component 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
unaected 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 congurations, 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 the following:
● Ensure the write lter is used properly 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.
● Never enable the Windows Page File feature.
● For use cases that require frequent writes, such as active system logging, call center phone and video
recording, and industrial logging, you should congure the thin client to write to a server. If local writes
are necessary, they should be done in the overlay cache. Please contact HP for help determining an
appropriate interval schedule for committing the overlay cache, or preferably log the data from the
overlay cache to a server.
If your use case requires non-standard write lter usage, please contact HP to ensure that your thin clients
are congured properly.
16 Appendix A Unied Write Filter