Tag Info

Hot answers tagged

51

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 ...


20

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 ...


18

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 ...


16

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

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 ...


12

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 ...


12

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) ...


12

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 ...


12

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 ...


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 ...


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 ...


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 ...


8

Yes, it works really well, but you have to get a 'fast enough' storage for this. It helps me a lot in my notebook. And it's good since I don't have to use a 7200 RPM HDD, nor waste money on SSD or something like this. I'm not made from money and a fast enough pendrive is dirt cheap now. Try it out with a friend's pendrive. (I'm running Windows 7 ...


8

Yes, ReadyBoost will help. But I think an 8 GB card will likely be overkill - with ReadyBoost, more is not always better. ReadyBoost works as an optimization for your existing RAM and page file. You're not storing or caching more information anywhere, you're putting the same information in a faster location. Your page file rarely grows as large as ...


8

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 ...


7

Don't be too concerned about the packaging. Many products sold in bulk or as OEM or as budget level forgo any fancy packaging as part of lowering the price of the product. This is especially true of electronics and computer products. It should not usually be considered relevant to whether or not a product is new (although sometimes it is an obvious sign). ...


7

Here's a KB article on the issue: http://support.microsoft.com/kb/120138. There is a certain file limit on the root directory of FAT file systems, which SD cards typically use. This is why camera manufacturers store them in sub-directories, as you pointed out.


7

How easy it would be to break this setup (to decrypt the root filesystem and make it boot from any sd card)? How hard it is to "break" your setup depends on the number of bits of entropy in whatever method you're using to sign/encrypt the filesystem itself (as this determines the total number of unique combinations that can be used to brute-force the ...


7

I assume you are using a PC linux or mac computer to perform the copy, not the raspberry pi itself. You will probably need to add a block size. I have seen one and four megs used for Raspberry pi disks by specifying bs=1M or bs=4M. I think block size is more important when writing the disk as large transfers are quicker than smaller ones. This does not set ...


6

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 ...


6

Given that the problem shows up at filesizes of 4GB what file system is in use on the card? If it is FAT32 the problem you are seeing might be caused by FAT32 having an upper file size limit of 4GB. See http://en.wikipedia.org/wiki/File_Allocation_Table#FAT32 for more information On Windows you can identify the file system by right clicking on the device ...


6

Well, why. There RAID on SD cards. For example, for those who collect mobile robotics. MS robots & mechanical men The Pocket Mini Computer Well, remember that this is just P8X32A 8 cores, that does not compare like with Tilera). In general, it is more like an example. Get 64GB CompactFlash--via 4 microSD cards PhotoFast's CR-7200 ...


6

Don't store them below -40 °C or above +100 °C (for example, a car dashboard in some places). You can theoretically damage them with a severe enough impact. 2000 g or more might be enough. Don't short the pins, or use them in space. Don't use them for long term archival purposes - in 500 years several of the compounds will have ...


6

Given software support, any SDHC card reader is capable of reading SDXC cards. From Secure Digital # SDXC - Wikipedia: Compatibility with SDHC [...] SDHC host devices will accept SDXC cards that follow Version 3.0, since the interface is identical, but the following issues may affect usability: SDXC cards are pre-formatted with Microsoft's ...


6

Most SD cards do come pre-formatted. Assuming there was a previous user, if they only did a quick format, then the file table was wiped but not that actual data, meaning that just about any forensic toolkit (e.g. Encase or FTK) will be able to tell you if there's anything there. However, if they did a full format, then there is no publicly known method for ...


6

Wikipedia's article about Secure Digital (SD) says this : The power consumption of microSD cards varies by manufacturer, but appears to be in the range of 66-330 mW (20-100 mA at a supply voltage of 3.3 V). Specifications from TwinMos technologies list a maximum of 149 mW (45 mA) during transfer.[21] Toshiba, on the other hand, lists ...


6

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 ...


5

ReadyBoost is a reading file cache, it is not an extension of virtual memory, that is based on the fact Flash memory has effectively zero seek time to cache small files (because Flash memory is also slower at sustained write that you HDD). What ReadyBoost also does is provide more space for the Windows Super Fetch function, if you don't have any ReadyBoost ...


5

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 ...



Only top voted, non community-wiki answers of a minimum length are eligible