[mdlug] ReadyBoost (was: Suggestions for flash-drive Linux?)

[David Favro]

Richard Herrell wrote:
> Readyboost simply replaces hard disk reads and writes with flash reads 
> and writes by caching portions of the paging file onto a flash disk:
>
>  From the FAQ:
>
>      Q: Isn't this just putting the paging file onto a flash disk?
>      A: Not really - the file is still backed on disk. This is a cache - 
> if the data is not found in the ReadyBoost cache, we fall back to the HDD.
>
>      http://blogs.msdn.com/tomarcher/archive/2006/06/02/615199.aspx
>   
I read the whole interview, and found this very interesting because,
while he doesn't unequivocally say it, he seems to imply that ReadyBoost
is indeed *only* a pagefile cache, while I had been lead to believe that
it was a smart disk cache: Steve Gibson said here
http://www.grc.com/sn/SN-068.htm (search for ReadyBoost) that Vista
would gather together many of the (presumably rarely modified) files
used for bootstrapping and put them into the flash drive for faster
*reads* on boot.  This makes a little more sense to me than the
swap-to-flash which I have always thought was of dubious value for the
reasons already mentioned previously in this thread (your money is
better spent on volatile RAM so no swapping is needed + it will kill
your flash).  Having your boot environment on flash might speed up boot,
especially many small files requiring seeks, and since they would not
require re-writing the cache (often), it won't shorten the life of the
flash.

I don't care much since I don't use Windows, but does anyone have a
definitive indication that ReadyBoost has nothing but paged-out RAM in
the cache (which helps little on boot unless it can be used in some way
to restore previous state as in "hibernate"), as opposed to additional
parts of the filesystem or other data that aids the boot?  It seems odd
to use non-volatile memory for data that doesn't need to be retained
across power-cycles.

-- David Favro