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dual partition formatting back to single retains first partition

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Offline Mlapse

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i just wanted to share this because i thought it was strange..is it me? :)

had this sd card that has been used in a S95 dual partition setup for a long time.
never had a reboot failure.
end of last year i reformatted it in the camera, placed it in the pc reformatted the single partition fat32 with fat32format for use in my g1x and created the boot flag in camera since it was single partition now.

this worked for a while, but today i noticed that yesterday it got stuck on the reboot, lens had not moved out and led was still flashing 'busy'.
since there was no obvious reason, it had succesfully rebooted a few times before, voltage was good...reboot flag was still set: after pulling and reconnecting the power script started running.
speed of card on the pc was also good.
so no obvious reason why it had failed.

i decided to reformat it back to dual partition, but now with the dual partition software for the s110-102b, so i placed the build on the single partition fat32 card.
after the cam had created dual partition and placing it in the pc to load the s110-102b build on both partitions.
the first partition already contained CHDK files.
i thought it was strange but decided, without first placing the s110 build on both partitions, to start up chimp to make the card bootable since dual partition boot can't be made in cam as far as i know.
and then chimp told me the build on the fat partition was 1.5 from the s95. ...and appeared to have the boot flag set since chimp only gave the option to remove it.

i checked that and yes, the first partition had the s95 software that i thought was destroyed (at least the tables referring to it) when i reformatted the card back to one partition in camera and then again with fat32format and after it has been used for a few month as such i would have expected it to be at least overwritten at some point.

 
« Last Edit: 28 / June / 2022, 17:20:41 by Mlapse »
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Offline philmoz

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Re: dual partition formatting back to single retains first partition
« Reply #1 on: 28 / June / 2022, 18:35:55 »
SD cards do wear levelling in their firmware to write to unused blocks first before overwriting previously used blocks.
On a large card it is quite feasible that the entire first partition remained intact as you described.

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Offline c_joerg

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Re: dual partition formatting back to single retains first partition
« Reply #2 on: 29 / June / 2022, 02:29:57 »
But maybe the memory of the second partition was never released...
I've also experienced strange things. Even exFAT to FAT32 or vice versa was not always unproblematic.
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Offline Mlapse

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Re: dual partition formatting back to single retains first partition
« Reply #3 on: 29 / June / 2022, 02:45:27 »
i thought so too, checked that and it was added to the single partition....at least according to windows. and apparantly it wasn't overwritten while that location only had one or two writes since it was the boot partition, seeing that all other space was used at least a dozen times i would expect it to have written first on that location that only had at most a few writes done....but that's just my thought.

even then i think it's more odd that the first partition files and bootflag were magically restored after reformatting it to dual partition in camera. data retrieval is usually a lot harder in my experience.
« Last Edit: 29 / June / 2022, 03:07:41 by Mlapse »
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Offline Caefix

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Re: dual partition formatting back to single retains first partition
« Reply #4 on: 29 / June / 2022, 10:23:05 »
... when i reformatted the card back to one partition in camera ...  :blink:
I would expect only the active partition to be reformatted.

Quote
//gui.c ~815
#if CAM_MULTIPART

static void card_break_proc(unsigned int btn)  :haha
...
ThereĀ“s no unbreak_card(>:() feature in cam...
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Offline Mlapse

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Re: dual partition formatting back to single retains first partition
« Reply #5 on: 29 / June / 2022, 11:03:57 »
yes, it only shows the volume of the active partition when canon asks you if you want to format, but after format it will show the volume of the whole card and subsequently you can format that on a pc if you don't like the exFAT format.
to me it appeared to be the quickest method to get a card usable again as a single partition. arguably not the best ;)

i thought there was a mention somewhere here how to turn a dual partition card back to one
https://chdk.fandom.com/wiki/Prepare_your_SD_card
but it must have been in my attempt to write a 'prepare your sd card instruction' probably got it from here:
https://chdk.setepontos.com/index.php?topic=3490.msg35200#msg35200


« Last Edit: 29 / June / 2022, 11:19:19 by Mlapse »
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Offline Caefix

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Re: dual partition formatting back to single retains first partition
« Reply #6 on: 29 / June / 2022, 11:24:44 »
Sounds like "Free Partition Manager" could do it...  :)
https://download.cnet.com/developer/Amazing-Share/i-10320712/
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Offline Mlapse

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Re: dual partition formatting back to single retains first partition
« Reply #7 on: 29 / June / 2022, 11:32:57 »
my other method involves just removing the partitions in linux and then reformatting it....but haven't done that in years, it seemed to me like a lot of work that the cam could do in one go.
maybe that's also possible in windows disk manager nowadays, but never tried that.


Haven't tested though if i recreate dual partition in camera after removing partitions if the files would also return
« Last Edit: 29 / June / 2022, 11:46:37 by Mlapse »
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