A hard drive-based JACE-NXT does not use EWF, by default. However, you can manually configure such a unit to use EWF on drive partition C. For related details, please contact Systems Engineering.

The Windows XPE operating system installed on CompactFlash based JACE-NXT models makes use of an “Enhanced Write Filter” (EWF) to protect the flash from excessive write transactions. This prevents premature failure of the flash memory. The EWF redirects file writes/modifies/deletes to an “overlay” located in RAM. Upon an orderly reboot, these overlay changes can then first be “committed” to persistent flash storage, or in cases where thought to be undesirable, be discarded.

By default, EWF is enabled only on two partitions of a flash-based JACE-NXT (C: System, and E: History), as the third Niagara (D:) partition does not need EWF overlay protection. Typically, Niagara writes occur only upon a station save, or if installing module jar files. These are low frequency writes as compared to various Windows file writes to the System (C:) drive or writes to the Niagara History (E:) partition.

Explicit EWF commands are used on these two partitions to either commit overlay changes to flash or to discard them. Any flash-based JACE-NXT provides related Start menu commands, see Figure 35.

EWF operation in a flash-based JACE-NXT differs from EWF operation in the predecessor JACE-NXS controller, which always committed changes to flash drive partitions upon an orderly reboot. Thus, the EWF commands shown in Figure 35 are new to the JACE-NXT.

You typically access these commands using a remote desktop connection to the JACE-NXT. They are also available when you have a local console attached to the unit. For more details, see the following sections: