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65

Flash memory indeed has limited write cycles. However, by now it is unlikely that you'll encounter this within the normal lifetime of such a card. Usually this is in the order of 100,000 write cycles today and SD cards include circuitry to manage wear-leveling, that is, spread out writes over the storage media evenly to avoid "hot spots"—pages that are ...


59

You could try pressing the card together (in case it came a little loose?) and maybe cleaning the contacts with a little bit of isopropanol on a swab. But I really wouldn't expect any results, and at best you might manage to read some of the data off before it dies again. I would not recommend opening it up under any circumstances - that will not help ...


33

On newer MacBook Pro's the SD card slot is no longer exposed as a USB device. Because of this you'll need to attach the raw device to the VM in order to gain raw access to the whole card. Full documentation is in the Advanced Storage Configuration section of the VirtualBox documentation. As clearly stated in the docs: Warning - Raw hard disk access is ...


30

From man hdiutil: /dev/rdisk nodes are character-special devices, but are "raw" in the BSD sense and force block-aligned I/O. They are closer to the physical disk than the buffer cache. /dev/disk nodes, on the other hand, are buffered block-special devices and are used primarily by the kernel's filesystem code. In layman's terms /dev/rdisk goes ...


26

Durability In my experience, memory cards are quite durable, though occasionally finicky when it comes to formats. I recently ran a cellphone through the washing machine (it was so dirty), and the 2 GB microSD card works just fine in my new phone (I eventually got the washed phone working too, but it was a good excuse to upgrade). Rob Galbraith, who ...


20

Never trust FLASH memory of any kind for long term storage. My experience with FLASH is integrity begins to falter in as little as 5 years. The voltages stored in the FLASH memory cells dissipate and can be misinterpreted after a while. High temperatures will accelerate the dissipation and shorten storage even less than 5 years. High density FLASH where ...


20

The Internet. Can read/write any number of times Every computer I've seen in the past five years has either Wi-Fi built-in, or is a big workstation/server that's parked somewhere with a gigabit-or-better Ethernet cable sticking out the back There's no limit to how much data you can put on the Internet The data-rate limit of the Internet basically comes ...


19

Any SD card has a class-rating. It is printed on the card, usually prefixed by HC. Class 10 (HC10) is currently the standard for FAST SD cards. Multiply Class by 1 MB/s to get the minimal transfer-speed. Class 10 is 10 MB/s. A normal (slow) sata HD can easily do 120 MB/s. Conclusion: A SD card is so MUCH slower than the harddisk that comparing them is ...


17

Photorec is designed specifically for this. It looks at file headers for various well known files and recovers photos - it does however mangle up filenames so you may need to rebuild these from exif data. CGsecurity also has an application called testdisk for whole drive recovery, which the OP ended up using. This is useful where you know the disk is in ...


15

If you read the SD Specifications Part 1 Physical Layer Simplified Specification, section 4.3.6 "Write Protect Management" says Three write protect methods are supported in the SD Memory Card as follows: - Mechanical write protect switch (Host responsibility only) - Card internal write protect (Card's responsibility) - Password protection card ...


15

Did you buy it from Amazon itself or from one of their (many) “associates”? If you bought it from an associate, then it is effectively no different than buying from someone on eBay (a lot of Chinese sellers on eBay will ship the item without its packaging so that they can offer free shipping). In that case, it could be in any condition, though of course the ...


15

I've managed to solve my own problem, but it is not exactly the simplest solution. In a nutshell, instead of storing files on the SD card, which of course Windows sees as a removable drive, it is possible to instead fill the entirety of the SD card with a virtual hard drive, which can then be mounted in Windows, and is treated as an actual hard drive. ...


14

If you're comfortable with using the Terminal, try this: First, look at the partition table by running this command: diskutil list You should see something like this: /dev/disk1 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *16.0 GB disk1 1: ...


14

A link to photorec was posted, but it only finds known file types. My files were of all random types. The nice thing, is photorec comes with testdisk. Using testdisk, I worked on the image I made with dd : # dd if=/dev/sdg of=~/tmp/sd.bin # sudo apt-get install testdisk #if on ubuntu/debian # testdisk ~/tmp/sd.bin (Select the partition) (Advanced) (Boot) ...


13

Kilobyte, megabyte and gigabyte mean different things depending on whether the international standard that one uses is based on powers of 2 (binary) or of 10 (decimal). There are three standards involved : International System of Units (SI) The modern form of the metric system and the world's most widely used system of measurement, used in both everyday ...


12

The x rating on an SD card is a measurement of read/write speed. 1x means a speed of 1.2 Mb/s, so 100x would mean a maximum speed of 120 Mb/s (or 15 MB/s). Whether or not this refers to maximum write speed or maximum read speed is vendor-specific.


12

Open the card device directly, and write 0x00 to it up to the capacity on the label. Write 0x55 0xff 0xaa to the first three bytes, and look for any non-0x00 byte up to the capacity on the label. If you find one, the card is either fake or defective. If you find 0x55 0xff 0xaa... definitely fake. dd if=/dev/zero of=/dev/mmcblkX bs=16M count=... echo -e -n ...


12

Answer for Windows 7 users Get the DeviceID of your SD card reader. You'll need a card in the drive, mounted by windows. Enter this command wmic diskdrive list brief It should look something like this: C:\Users\Sandy Scott>wmic diskdrive list brief Caption DeviceID Model Partitions Size WDC ...


11

No, unless the magnet is REALLY strong (see below quote). There is not enough magnetic material in them. "A magnet powerful enough to disturb the electrons in flash would be powerful enough to suck the iron out of your blood cells" If the above quote is the case you should not be working where you do. It is also a big myth that normal magnets can ...


11

SD cards are SSDs, it's the exact same technology, but because SD cards aren't built for the same purpose they don't include the required features like smart. There is no way to tell how long the SD card will last, because the required data isn't collected so there is no way to generate an estimate. If SD cards did have the relevant details you would use the ...


10

You get the Permission denied error, because you are not [root][1]. That sounds strange in the context of Cygwin, but it hits home. When you query your status (id) in a normally started Cygwin shell, you'll get something like that: $ id uid=1001(user) gid=545(Users) groups=545(Users),555(Remote Desktop Users),513(None) $ dd if=/dev/sda bs=1000 count=1 | wc ...


10

NAND - raw flash memory Raw flash uses its own protocol, and this protocol includes reading pages, writing pages, and erasing blocks. It does not work like disks - disks are able to read blocks and write blocks, flash is able to read and write pages - and a set of pages called a block must be erased before you can write new data. You can only erase a ...


10

The adapter is basically just a bunch of wires; they use the same signaling. The class of the device will determine the speed, not the adapter.


10

Excellent article about flash filesystems. Important question when talking about flash filesystems is following: What is wear leveling? Wikipedia article. Basically, on flash disks you can write limited number of times until block goes bad. After that, filesystem (if there is no built-in wear leveling management on hardware, as in case of SSDs there ...


9

It's definitely doable, but there are two concerns that you'll need to address if you want to boot and use Windows 7 off of an SD card regularly. Transfer speeds; a run-of-the-mill SD card is going to have mediocre read/write performance. I'd try to invest in a faster model. Any of the ones designed for SLR cameras (like SanDisk's Extreme line) should ...


9

NAND stands for Negated AND. It often refers to the way the a logic gate is build from silicon. Flash memory is also built from silicon chips and uses NAND gates. This leads to the term NAND flash. I suspect that this is the NAND you refer to, but for completeness sake I wanted to mention the background. You can build storage with NAND flash, but you will ...


9

At my work, we use SD cards in an embedded system. If we try to boot up with a card that is locked, we'll get a kernel panic. This wasn't a big deal until we got a batch of SD cards that had very loose write switches: the act of inserting the card into the reader was sometimes enough to move the switch and lock the card. A lot of people started trying to ...


8

If anyone sees this later: Someone wrote an open source tool called "F3" to test capacity of SD cards and other such media. It can be found here.


8

The accepted answer is right, but it doesn’t go into much detail. One of the key differences between /dev/disk and /dev/rdisk, when you access them from user space, is that /dev/disk is buffered. The read/write path for /dev/disk breaks up the I/O into 4KB chunks, which it reads into the buffer cache, and then copies into the user space buffer (and then ...



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