On 3/22/2013 6:57 PM, Chuck Norcutt wrote:
> Remember that the file system is still Microsoft FAT32. Small file
> clusters and lots of space but (eventually) still subject to the same
> old fragmentation problems as all earlier versions of FAT. If you
> merely delete files you will eventually cause fragmentation.
Three things.
1. I use until full, then erase or format. If I change cards before one is
full, say to be ready for a long day of
shooting that likely won't fit on the card in the camera, the process is the
same, full clearing of files before re-use.
That shouldn't cause this problem even if I only erase. Quite different case
than lots of random erasing and writing.
2. I was under the impression that the FAT the system/camera sees is virtual,
as the on-card controller moves stuff
around for load leveling. That means any fragmentation in the FAT is illusory,
and actual fragmentation is invisible.
3. I'm not sure sequential reads are meaningfully quicker than random reads or
even quicker at all. The random access
test in HDTune just shows a flat line for flash cards. There's no mechanical
component, just memory addressing - and, as
above, that access is always through an internal lookup (different FAT) hidden
to the outside world.
Am I wrong anywhere here? I know it's really easy to forget the load leveling
isolation of internal and external file
structures on these cards. The look exactly like physical HDs to our computers.
> It might take a very long time on a 32GB device but it will eventually get
> there.
Depends on how smart the load leveling firmware is, I would think. Completely
irrelevant in the special case under
discussion - all sequential writes, then full erase/format.
> Performance will also suffer although not as bad as on a mechanical
> disk. Erasing a file and allocating space within a fragmented disk are
> also much more complex operations. When voting on simplicity vs
> complexity simplicity will likely be more reliable in the end.
Still, we don't actually know what is where on the 'disk'. Any complexity of
calculations to decide what to put where is
apparently going on all the time, with every write.
> Dr (Flash) Disk always advises formatting in camera vs erasing images.
> He also recommends an occasional full format in the computer since it
> will verify correct operation of all parts of the card.
I don't believe that is necessarily true of a load leveling flash card. For all
we know, the full formatting could be
writing/reading more than once to some of the same physical locations and never
writing to others.
It's the job of the card controller to keep 'wear' even and note memory
locations that are failing.
> Follow that with format in camera to install folders the camera is expecting
> to see.
This is another safety rule that I think is no longer necessary. Would never
have been thought necessary, I"d guess,
were it not for Oly and Fuji and their issues with proper formatting and
reading of the now happily defunct xD cards.* I
know, I was there. :-( But I've just tossed new cards in various cameras
without formatting in the camera and - glory
be! - the correct directories appear with images in them when I take the cards
out.
Think about it. Are the camera developers idiots? Why, when it's not exactly
rocket science for firmware to create
directories it needs, would they make the whole process of taking and keeping
images with their products so fragile?
Nice way to lose market share.
These same ideas live forever on the web - check the dates of advice! - and get
repeated endlessly by those who don't
know any better and want to be beyond failsafe.
Of course, some idiots at Oly long ago, probably with the assistance/complicity
of Fuji and one or more card makers are
at least in part responsible for the sense that card formats are somehow
fragile. The xD card simply proved the
foolishness of trying to save a few pennies by putting the controller in the
camera, instead of the card. CF and SD have
never had such problems.
Yes, I understand that never erasing an image, except for the last one
recorded, makes the likelihood of recovery in
case of loss of the FAT higher, and I practice it. It would apply to any sort
of 'disk' is this particular use.
Dr. Leveled Flash Moose
* Although I still have a couple of cameras that use them, they are hardly ever
used. They work, and I'll never reformat
them.
--
What if the Hokey Pokey *IS* what it's all about?
--
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