Basic flash questions

D

Doug G

Now that we have our completed XPE systems in the field, our customer has
suddenly decided that they may not like having "rotating media" on the
factory floor, despite the fact that we based our product on the customer's
own existing device with a hard disk, and the specs for this project were
set about two years ago. Such is life...

I am not sure if this will happen since it will be a costly change, both
from a hardware and s/w development point of view. For one thing, they are
going to have to give up a lot of functionality. Since I have been running
with a 20Gb disk, I did not concern myself with footprint, so I installed a
lot of XP features that they are going to miss if I have to cut the
footprint (my current size is about 150Mb on the boot partition before FBA).

Anyway, since I was always developing for a disk-based system I did not pay
attention to most of the postings here about flash-based systems. I just
need some basic answers to the following so that I can evaluate the overall
feasibility and what it will take to do this. I did look at MSDN and some
archives and have a basic idea of flash specifics, but would like some
clarity.

1) Using an internal "flash disk" device, I can partition it into a
read-only system drive (EWF protection) and a read/write user partition,
correct?

2) I currently use disk-based EWF on our system. When using RAM-based EWF,
is there still that extra EWF-private partition like I have on the
hard-disk-based systems?

3) Does the ewfmgr "-commit" command work with RAM EWF? I guess I thought
that the commit took place on the next reboot, which would be difficult if
the overlay data is in RAM.

4) Do read cycles affect the life of flash memory, or is it only the write
cycles?

Doug G
 
S

Slobodan Brcin \(eMVP\)

1. Only if you have disk marked as non removable. (Or use dos fdisk).
2. You can skip creation of EWF private partition.
Browse www.xpefiles.com for ramewf.zip for component and description on how
to do this.
3. -commit does not work without EWF partition. But -commitanddisable will
work. Commit will write data on shutdown.
4. Only write cycles damage flash memories.

Regards,
Slobodan

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S

Sean Liming \(eMVP\)

I will add that most of the NG posts are about CompactFlash. There are
solutions from M-Systems and San Disk that have special flash drives that
interface to the IDE and be treated like a regular hard drive: partitioning,
format, etc..

Regards,

Sean Liming
XP Embedded Manager
A7 Engineering (www.a7eng.com)
Author: Windows XP Embedded Advanced and Windows NT Embedded Step-by-Step

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S

Slobodan Brcin \(eMVP\)

You are right, but they only use block remapping to reduce wear of same
physical flash block. But writes still physically degrade flash, although
you can do it probably more time then you can do it on HDD :)

So basically you can use it like HDD.

Regards,
Slobodan

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D

Doug G

Our solution, if we go this route, would definitely use an internal IDE
flash drive. I knew that I could treat it like a regular HDD, but was mainly
concerned about the number of write cycles. It looks like I might be able to
get away with that, which will make things pretty easy from my standpoint.

Thanks for your responses.

Doug G
 
D

Doug Hoeffel

Doug G.

I am also considering moving one of my partitions (not protected by EWF)
from a rotating drive to a 40-pin IDE SSD. (www.hsc-us.com). I don't think
you would need to worry about wearing it out. The drive I'm looking into
has implemented wear leveling technology (300,000 is erase / write per cell)
which spreads out the write area to ensure that the same cell won't be
written repetitively.

--
HTH... Doug H.
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S

Sean Liming \(eMVP\)

M-System has made the claim that EWF is not a requirement for their flash
devices. They have some white papers and/or information if you need to
convince internal magement and other engineers.

Regards,

Sean Liming
XP Embedded Manager
A7 Engineering (www.a7eng.com)
Author: Windows XP Embedded Advanced and Windows NT Embedded Step-by-Step

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D

Doug Hoeffel

Thanks Sean. The problem I have is primarily cost. I'm no expert on this
type of media but I have done some investigation and know that some SSD
makers have high-end devices that guarentee data integrity in case of power
failure without using battery backup. This is all fine and dandy but these
devices are tooo expensive. This is why I'm looking at a lesser drive where
I can get the benefits of non-moving parts, very small access times, no
cache etc. that is at a price point where I might be able to convince
management.

--
Doug
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S

Sean Liming \(eMVP\)

I understand. Cost is a big factore. The iDOC is a possible solution, but I
don't know if it is available. Some manufactures sell kits or flash
interface chips so you can build your own IDE flash drive. Just a thought.

-Sean
 

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