How robust is FBWF on FAT32 with random power disconnect?

  • Thread starter Thread starter jonah.peskin
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jonah.peskin

I'm curious if people have had much experience with using FBWF/FAT32
on a system that could be powered off at any moment (including during
booting)?

I have a system that does not have a power button/switch. As soon as
power is plugged in, BIOS is configured to boot. It is turned off by
pulling the power plug (The idea is it is part of a larger system that
is plugged into a power bar. The whole system is turned on/off via
one power bar switch).

I notice that before enabling FBWF using fbwfmgr, XPe on FAT32 can
often get corrupt files and report an error on next boot (e.g.
"corrupt file XXXXX.yyy.. run chkdsk") if power is unplugged suddenly.

So far, no corrupt file errors are reported when FBWF is enabled. But
so far I have only thoroughly tested pulling the power after the
system is fully booted.

With FBWF and FAT32, can I count on files not getting corrupted if
power is pulled AT ANY TIME?

Thanks
 
With FBWF and FAT32, can I count on files not getting corrupted if
power is pulled AT ANY TIME?
Click to expand...

No. I have tested this by pulling the power several hundred
on several machines times without a problem but I do get an
occasional failure in the field. In these cases the system is
repaired by the customer with a recovery disc.

It doesn't happen often enough to be a concern. The failure rate
is less than the failure rate of the hardware.
 
I have heard mixed feedback. Several customers are using NTFS (on CF card)
after seeing failures with FAT32 even with FBWF in place.

--
Regards,

Sean Liming
www.sjjmicro.com / www.seanliming.com
Book Author - XP Embedded Advanced, XP Embedded Supplemental Toolkit
 
An easy answer is 'yes'. That's what FBWF is for - to protect your image
(even in a sudden power loss). For sure having FBWF enabled will dramatically
reduce file corruption from a blackout. Depending on your choice and
configuration of filesystems though, there may be writes to the disk that are
generated below the FBWF filter - say NTFS transaction logging. These in
theory could corrupt. Not sure though that if corrupted, you would ever see a
"corrupt file" message though. Again in theory, I think NTFS would try to
roll back the last transaction if a power failure occurred during the
logging.
Maybe too much information (particularly given some of it is speculative),
but I highly recommend a write filter if you expect sudden power loss - even
if it doesn't come with a 100% guarantee.
 
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