On 03/10/2014 03:33 PM, Tomaso E wrote:
Thanks Dave for your post. It was very helpful, especially the link
to the unstable-bits article.
I have a follow-up question, if power is lost abruptly, does the
unstable bits simply result in lost data, or does the file system
become corrupted and could previously stored data get damaged? Or
does are the results unpredictable?
In my limited experience, the results are unpredictable. There was a
commercial flash file system a few years ago (I think the name was
FlashFX) but I could not get good answers as their system was "proprietary".
I think I might have to build a shield or external circuit as you are
considering doing, to provide continuous power to the unit in spite of
fluctuations in the external power supply.
Thanks again for your help!
Tomaso
On Monday, March 10, 2014 3:56:07 PM UTC-4, David wrote:
On 03/10/2014 02:43 PM, Tomaso E wrote:
> Hi All,
>
> I'm considering using a Beagle Bone Black for a project that I am
> working on. I have some basic experience working with a couple of
> different microcontrollers/computers but I really like the specs of
> the Beagle Bone Black. I love that it can run various Linux
> distributions and the hardware profile matches my project
requirements
> pretty closely.
>
> One concern that I have is regarding the Beagle Bone Black's
ability
> to tolerate a sudden loss of power. On many embedded Linux
systems,
> if power is lost abruptly, the file system can become corrupt,
and the
> device will not be able to boot, unless the file system is
completely
> rebuilt.
With rotating media, journaling file systems such as ext3/4 handle
sudden asynchronous power losses fine. The problem seems to be that
flash sub systems such as SSD/eMMC contain internal controllers which
handle wear leveling/bad-block management etc. Here the issue becomes
worse as the file system has no knowledge of these internal
processes. I
have worked with native flash file systems such as UBIFS, but they
also
suffer from phenomena such as "unstable-bits"
http://www.linux-mtd.infradead.org/doc/ubifs.html#L_unstable_bits
<http://www.linux-mtd.infradead.org/doc/ubifs.html#L_unstable_bits>.
For these reasons, I am in the process developing a cape which
provides
short term battery backup and intelligence to perform an orderly
shutdown. Other features include an independent watchdog and POE
supprt.
>
> Can the Beagle Bone Black tolerate an abrupt loss of power and
not be
> bricked? Ideally, for my project, the device would be powered down
> properly, but I can think of instances where the board might lose
> power suddenly. I was wondering if I would have to worry about
having
> the device get bricked if this happened.
The BBB would not be "bricked", but any file systems on the
eMMC/SD may
be corrupted.
>
> Thanks in advance!
> Tomaso
>
>
HTH,
Dave.
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