Download page Unified Write Filter (UWF).
Unified Write Filter (UWF)
Menu path: Setup > System > Unified Write Filter
The Unified Write Filter (UWF) is the write filter in Windows 10 IoT. The UWF intercepts all I/O write attempts and forwards them to the overlay buffer. The overlay buffer is an area in the RAM. Thus, the programs running on the device do not access the flash memory of the device. In this way, the operating system is protected from changes. All changes are discarded when the system is rebooted.
The behavior of the UWF with regard to the overlay buffer can be configured in IGEL Setup.
You can find further information on the Unified Write Filter on this page at the Microsoft Developer Network.
Be aware of the write filter exclusion rules: https://docs.microsoft.com/en-us/windows-hardware/customize/enterprise/uwfexclusions.
UWF status display in the taskbar
- UWF enabled: Locked padlock symbol.
- UWF disabled: Unlocked padlock symbol.
Settings in IGEL Setup
- Use IGEL Setup for UWF settings
☑ UWF settings are configured in IGEL Setup. (Default)
☐ UWF settings are configured in another manner.
- Enable UWF
☑ The write filter is enabled. (Default)
☐ The write filter is disabled.The Unified Write Filter must be enabled during regular system operation. IGEL does not provide support services if the write filter is disabled.
- Warning threshold for UWF: A warning is issued when the buffer exceeds this size (in MB). The user is prompted to save his data, close all programs, and restart the device. (Default: 512)
- Critical threshold for UWF: Normal operation is no longer possible when the buffer exceeds this size (in MB). A dialog is displayed; the user is prompted to save his data immediately. When the dialog is closed, the device is restarted. (Default: 900)
Maximum Overlay size for UWF: Maximum size for the temporary buffer for saving writes. (Default: 1024)
The actual size of the overlay buffer changes during runtime according to the memory requirements of the data to be written. The remaining physical RAM space is available to the system as regular RAM.Avoid very high values for the maximum size of the overlay buffer. With increasing maximum size, the probability of a conflict between overlay buffer and regular RAM demand rises. The behavior in case of conflict depends on the firmware version in use. IGEL WES 4.01.100 or older: There is no guarantee that the maximum overlay size is available at any time. Thus, it can happen that regular RAM usage and overlay buffer together require more physical RAM than is available. In this case, system failure will occur. IGEL WES 4.02.100 or newer: The RAM usage is monitored periodically. As soon as the margin between the currently required regular RAM space and the maximum overlay size has decreased to a threshold (default: 250 MB), a message is issued. The user is prompted to restart the device as soon as possible.
List of directory excludes: Insert directories that you want to exclude from the Write Filter here, in order to allow writing to these. Use the complete path, including the drive letter.Please note that also write accesses to memory locations increase the Write Filter's RAM demand. This is a property of the Windows Write Filter and therefore systemic.
To create an entry, click .
To remove an entry, click .
To edit an entry, click .
To copy an entry, click .
List of registry excludes: Insert registry keys that you want to exclude from the write filter here, in order to allow writing to these. Use the full key path.Please note that also write accesses to memory locations increase the Write Filter's RAM demand. This is a property of the Windows Write Filter and therefore systemic.Directory and registry excludes defined by IGEL and needed for system operation are not shown and cannot be edited.