EWF partition size query!



Hi all,

I am using a 512 MB compact Flash to run my XP Embedded OS. My RAM size is
also 512MB. Right now i am using the whole CF as a single partition and it is
EWF protected on RAM Reg Mode. My post FBA image size is around 220 MB. I
have configured EWF partition size as 64MB.

My question is how do i freeze on EWF partition size?

In future i am planning to have 3 partitions on my CF out of which 2 will be
EWF protected.The unprotected partition size will be around 150 MB and this s
going to be a data segment. The other two protected partitions will have OS
and all application softwares.

How can i optimize on the size of EWF partition size? Is there any means of
checking the utilization of EWF overlay?

Please help!




It was not clear from your post what you refered to as "EWF partition". And "freezing on EWF partition size" wouldn't make sense if
you talked about the EWF Config partition.

With EWF RAM Reg mode you don't have EWF config partition at all. The EWF states are configured and stored in registry.

In case you are referring to EWF Overlay in RAM the below makes sense (it is not a partition though). Unfortunately, there is no
currently a way to limit the size of the overlay. It can grow as much as you have RAM available. If you really need to limit the
overlay, you should take a look at new FBWF of FP2007.

There is a topic in documentation for SP2 and FP2007 where they dicuss how to minimize the overlay size on a running XPe image if
EWF RAM Reg mode is used.
Here is also another page that will give you some tips on how to do that: http://msdn2.microsoft.com/en-us/embedded/aa731207.aspx


Hi KM,

In EWF components settings, what is EWF Partition size? I have been setting
it to 64 MB even when i chose RAM Reg Mode... You mean to say this makes no
sense in RAM reg mode?

I always thought this is the size of EWF Overlay in RAM on run time image!
Please correct me if i am wrong,




Unfortunately, that size is for EWF Config partition that is not going to be there with EWF RAM Reg mode (only EWF Disk mode). That
size can't be even changed for EWF RAM overlay (not Reg). I mean EWF FBA component will initialize and create the EWF config
partition for RAM mode with a predefined (small) size.

I guess it should gray out the partition size when you select the EWF RAM modes. Well, hope it is going to be fixed in future
versions of the component.

Here is the steps described how you configure EWF RAM Reg mode in TD: http://msdn2.microsoft.com/en-us/library/ms940182.aspx

Matt Kellner \(MSFT\)

The EWF partition size setting in the EWF ConfigUI only applies to DISK
mode, where it sets the size of the EWF volume and thus the maximum amount
of write information that can be stored there. In both RAM and RAM-Reg
modes, the partition size is essentially meaningless (in RAM mode, it will
still set a partition size, but this partition does not actually get used to
store any data and has no bearing on the operation of RAM mode. In RAM-Reg
mode, this setting is ignored completely.)

EWF RAM and RAM-Reg modes keep their overlays in system memory, and the
overlay grows dynamically with the captured writes. Unfortunately, the OS
has no knowledge of EWF's usage of memory and thus does not have a way to
protect against memory filling up.

If you need a write filter only to protect against file-system writes (as
opposed to ALL possible writes to the media), you should consider using
File-Based Write Filter (FBWF), introduced in Feature Pack 2007. FBWF
supports a set threshold for write information and offers better flexibility
for various write-protection scenarios.

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Similar Threads