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dahlfors

A tip about CF/SD memory cards and broken partitions

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I read this quote in the locked Lexar memory card topic:

"The card was corrupted so badly that computer/rescue software's only recognized it as 7,60gb drive... Even that it is 128gb card. Tried to format it with panasonic, canon and sony cameras, nothing. With computer and all formatting methods, nothing. So totally destroyed card. Just rubbish."

Since noone else mentioned it in the thread, I thought I'd mention it: THIS IS PERFECTLY NORMAL BEHAVIOUR. (Teemus card most likely wasn't broken at all - it just had garbage data in the middle of the partition which cameras and operating systems interpreted as end of partition - or made them hang).

So, Windows has no builtin partition management if you have broken the partitions (or managed to garbage the data by removing the media mid-writing) on any USB flash media or CF/SD cards. I'm not sure if MacOS has the ability either in this case. However, Linux has tools for fixing these issues (and I've had to turn to Linux a few times to fix my media after experimenting with them too much...).

In case you'd have partitioned a CF/SD card with just 8 GB - then all windows will be able to do is to recognize that 8 GB. However, in Linux you can remove that partition and create a new one spanning the full card, 64 GB, 128 GB or however big it is. After remaking these partitions, you'll be able to format the full card in Windows / MacOS or in camera.

Hope this might help some of you in case you break your flash media partitions...

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21 hours ago, dahlfors said:

I read this quote in the locked Lexar memory card topic:

"The card was corrupted so badly that computer/rescue software's only recognized it as 7,60gb drive... Even that it is 128gb card. Tried to format it with panasonic, canon and sony cameras, nothing. With computer and all formatting methods, nothing. So totally destroyed card. Just rubbish."

Since noone else mentioned it in the thread, I thought I'd mention it: THIS IS PERFECTLY NORMAL BEHAVIOUR. (Teemus card most likely wasn't broken at all - it just had garbage data in the middle of the partition which cameras and operating systems interpreted as end of partition - or made them hang).

So, Windows has no builtin partition management if you have broken the partitions (or managed to garbage the data by removing the media mid-writing) on any USB flash media or CF/SD cards. I'm not sure if MacOS has the ability either in this case. However, Linux has tools for fixing these issues (and I've had to turn to Linux a few times to fix my media after experimenting with them too much...).

In case you'd have partitioned a CF/SD card with just 8 GB - then all windows will be able to do is to recognize that 8 GB. However, in Linux you can remove that partition and create a new one spanning the full card, 64 GB, 128 GB or however big it is. After remaking these partitions, you'll be able to format the full card in Windows / MacOS or in camera.

Hope this might help some of you in case you break your flash media partitions...

Okay, didn't know this...

Also want to update status on the case of my Lexar card. (Old topic got locked so can't put it there) It will be sended over to Lexar laboratory at UK. Below is straight copy from email they sent me.

Regarding our data recovery process, we will take your card back and attempt recovery for you in our East Kilbride lab in the UK. If this is successful, the recovered data will be sent on DVDs or copied onto your replacement card and sent to you that way.

Should the recovery not be successful in East Kilbride, we will send the card on to our headquarters in Milpitas, California, where it will be dismantled so the NAND can be accessed directly. This process can take up to 12 weeks.

Please note, image recovery service is a courtesy for our Lexar Professional customers and is not part of our warranty. The recovery process does not guarantee the recovery of images as the nature of data loss on flash technology can vary.

The card will be replaced under the warranty but during the recovery process, the original may be destroyed.

So... time will tell what is the conclusion on this case.

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I would say this used to be the case when cards was still block devices.Meaning the OS could freely just read any block of data and all would be good. Even if power died during a write you could recover what's left.

But as with SSD cards now have a controller, a chip or two and more space then used. Then data is handled with wear leveling and whatnot just like an SSD. So if you pull the power you could corrupt that table of wonder and what's left is a garbled unreadable mess, cause it was never linear to begin with. And at this point the card won't let you do anything or at best read some small part of it.

At least that is how I understand it.

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19 hours ago, no_connection said:

But as with SSD cards now have a controller, a chip or two and more space then used. Then data is handled with wear leveling and whatnot just like an SSD. So if you pull the power you could corrupt that table of wonder and what's left is a garbled unreadable mess, cause it was never linear to begin with. And at this point the card won't let you do anything or at best read some small part of it.

As far as I know, the controllers are all closed source and there is no public detailed information on exactly how the controllers work from different manufacturers. Despite that we can't know how it works for sure, it would not make sense to design the controller so the media itself wouldn't be able to handle power loss or removal. Otherwise the manufacturers would start getting large return rates. Same method as is used on journaling file systems should work perfectly fine for wear leveling of flash memories, at a very small storage cost. This would mean that you would see data corruption (corrupt files, broken partitions / file system), but still keep a working flash card / SSD.

Have you heard of flash media behaving like you describe after power loss on write? 

 

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On 5/29/2017 at 9:34 PM, Teemu said:

Okay, didn't know this...

Also want to update status on the case of my Lexar card. (Old topic got locked so can't put it there) It will be sended over to Lexar laboratory at UK. Below is straight copy from email they sent me.

Regarding our data recovery process, we will take your card back and attempt recovery for you in our East Kilbride lab in the UK. If this is successful, the recovered data will be sent on DVDs or copied onto your replacement card and sent to you that way.

Should the recovery not be successful in East Kilbride, we will send the card on to our headquarters in Milpitas, California, where it will be dismantled so the NAND can be accessed directly. This process can take up to 12 weeks.

Please note, image recovery service is a courtesy for our Lexar Professional customers and is not part of our warranty. The recovery process does not guarantee the recovery of images as the nature of data loss on flash technology can vary.

The card will be replaced under the warranty but during the recovery process, the original may be destroyed.

So... time will tell what is the conclusion on this case.

That's a good customer service on their part. I wonder if Sandisk is equally good ? Has anyone here had a similar experience with Sandisk?

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I have had flash devices just die, but have not powered off any while writing. Not about to test ether.

However if it had behaved like a block device to begin with we would not have these problems, yet here we are with many ppl ending up with bricked storage devices for no apparent reason.
I would add that corrupt data is fine, and simple file systems like fat32 is easy to work with. But here the card itself have been corrupt and can't seem to be talked to. That shows  a level beyond a simple addressable block device.
I agree that the solution seems so simple, with just a little safety added and things should be smooth sailing. SSD kinda sorta took their time but seem to be more resilient nowdays. Flash memory still seems as fragile as ever.

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17 hours ago, no_connection said:

I have had flash devices just die, but have not powered off any while writing. Not about to test ether.

Any component issue in the storage controller will have the effect that the storage media goes dead. That does not matter if there is wear levelling or not, so there is no way for you as a user to tell if controller just had bad components, or if it would have been something related to wear levelling in the controller that made it die. The component death issue applies to SSDs and traditional hard disks controllers as well. With older hard disks the controller components were fairly large so that people skilled with electronics could exchange the controllers. On SD, that is a very complex task.

Anyway, I had a quick look around. The SD specs do not require the cards to be able to function on power loss at writing. However, while it is not in the specifications, many manufacturers apply methods against it. Which methods they use are unknown, but the methods that would make most sense are either journaled writing or a battery backup that can last for as long it is needed to ensure that power loss doesn't break the wear levelling system. Suffice to say, you are not likely to see these things handled properly on the cheapest of the cheapest cards. I found information that Sandisk had stated that they use some kind of protection against this, but they wouldn't state what methods they apply. I didn't search further for other manufacturers, since Sandisk is the brand that I've kept using.

 

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In such cases, I'd create an image file of the SD card (with any USB Image Tool for either PC or Mac). The image file should be the same size as the SD card (like, 128 GB, even if card reader doesn't see more than 8 GB). Then one can recover SD card's contents (and see all those GBs that he can't see otherwise). I recovered my files with https://restore.media/ online tool, but there are other tools to recover them with, e.g. recover_mp4 or the like. However, the best way to keep SD card's contents safe is to format it regularly (before any important recording). 

 

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