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EWF RAM Mode

  • Article

5/10/2007

EWF RAM mode uses the following configuration:

  • The EWF Overlay type is stored in RAM
  • The EWF volume is stored on disk

The EWF RAM overlay stores the write cache in RAM. When EWF RAM mode is configured during the First Boot Agent (FBA) phase, the EWF volume is created in available space on media. The EWF volume stores the EWF master volume table and an overlay stack that points to the overlay data in system memory. When you shut down the target system, the overlay data in system memory is lost. EWF RAM mode supports only one overlay level.

Use EWF RAM mode in the following scenarios:

  • Protecting data on a read/write volume from being altered or corrupted
  • Deploying a run-time image on a stateless device
  • Deploying a run-time image on a device without persistent read/write storage

The following diagram shows an example EWF RAM mode configuration.

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EWF RAM overlays require additional RAM to store the write cache. RAM is not pre-allocated by EWF; therefore EWF uses free RAM until the system runs out of memory. RAM requirements for the EWF RAM overlay vary. They depend on the amount of write operations that are made to the overlay. It is recommended that while you test your run-time image, you review the memory usage of your applications in Windows Task Manager.

Note

EWF allocates space for the RAM overlay from physical RAM pages, and can surpass the standard Windows non-paged limit of 256 MB. However EWF does allocate a small amount of space from the non-paged memory pool. Non-paged RAM size is typically less than 1.5% of the size of the RAM overlay, and the non-paged RAM usage is less than .2% of the total usage.

For more information, see Configuring EWF RAM Mode.

EWF RAM Reg mode is a type of RAM overlay that does not require an EWF volume to be present on the system. The metadata information that is normally kept in the EWF volume is instead stored in the registry. For more information, see EWF RAM Reg Mode.

The minimum EWF volume size for EWF RAM mode is 64 KB.

See Also

Concepts

EWF RAM Reg Mode
EWF Definitions

Other Resources

EWF Modes
CompactFlash
Bootable CD-ROM