Single Instance Storage - WIMs

Question

Consider this:
You update a WIM file which is fairly large.  You have 300 DP's, and until any particular DP receives the changes, you'll get a "hash value is not correct" on any OSD task sequences using that WIM.
Someone came up with the idea:
Have two different WIMs that you rotate.  Have Image A assigned to the task sequence, and update Image B when you have a change.  Once Image B is everywhere, change the task sequence to use Image B.  Next change to the image goes to Image
A.
Well, it seems both Single-instance storage along with re-transmittal doesn't work.  here's what I did:
Add a new OS image with a path such as this:
\\SCCM\Share\Win7.wim
Add this file to a distribution point, wait for it to appear
Create a new OS image with the *exact* same path
Add it to the same DP.
Both the file transmits (even though it's already there) and the file is stored in SCCMContentLib *again*.
So, I'm really trying to prevent the WIM from transmitting over the WAN again, and I certainly don't want it stored twice.  Is DeDuplication not applicable to WIM files?  Just Applications/Packages/Drivers?  Does it de-dup after the fact?

Answer 1

From the blog post Torsten linked:
"For the scenario where the admin creates and distributes a new OS image package by updating some properties of an already existing OS image (WIM format), although only changed file blocks will be sent to the remote server when the “Enable Binary Delta Differential”BDR
option is enabled for the package, the entire changed file will be stored in the content library, even though the original and the revised WIM file differ only by a few blocks. When Data Deduplication is used in the same scenario, only a few
extra blocks will be used to store the new data instead of the entire file."
With that in mind, it seems that even though your two WIM files are from the exact same source path, what gets transmitted to the DP is unique enough that it must store two copies.