HP T5720 Quick Reference Guide for Microsoft Windows XPe-based Thin Clients - - Page 35

Enhanced Write Filter Manager The Enhanced Write Filter Manager provides a secure environment for thin client computing by protecting the thin client from undesired flash memory writes (the operating system and functional software components reside in flash memory). The write filter also extends the life of the thin client by preventing excessive flash write activity. It gives the appearance of read-write access to the flash by employing a cache to intercept all flash writes and returning success to the process that requested the I/O. The intercepted flash writes that are stored in cache are available as long as the thin client remains active, but are lost when you reboot or shut down the unit. To preserve the results of writes to the registry, favorites, cookies, and so forth, transfer the contents of the cache to the flash on demand using the Altiris Deployment Solution software or manually using the Enhanced Write Filter Manager. After you disable the write filter, all future writes during the current boot session are written to the flash with no further caching until reboot. You can also enable/disable the write filter using the command line. Always enable the writer filter after you have made all of your permanent changes. The administrator should periodically check the status of the cache and reboot the thin client if the cache is more than 80 percent full. CAUTION: Never disable the write filter cache if it is more than 80 percent full. Access to the Enhanced Write Filter is limited to the Administrator account. NOTE: To avoid flash corruption when administering the thin client for permanent changes, HP strongly recommends that you disable the write filter cache before making permanent modifications to the system. Remember to enable the writer filter after making all of your changes. The following section describes how you can manipulate the write filter through the command line. Enhanced Write Filter Manager command line control CAUTION: Terminal Administrators should use Microsoft Windows NT file security to prevent undesired usage of these commands. When using the -commit command, all the temporary contents are permanently written to the flash memory. NOTE: Because the Enhanced Write Filter Manager commands are executed on the next boot, you must reboot the system for the command to take effect. Windows XPe includes the Enhanced Write Filter (EWF) console application command line tool, Ewfmgr.exe, which you can use to issue a set of commands to the EWF driver, report the status of each protected volume overlay, and report the format of the overall EWF configurations. By including the EWF Manager console application component in your configuration and building it into your image, you enable use of Ewfmgr.exe and the corresponding commands. To use the Enhanced Write Filter Manager using the command line: 1. Select Start > Run > Open. 2. Type CMD in the Open field to access the system DOS prompt. 3. Click OK. ENWW Enhanced Write Filter Manager 29