Articles by Our Experts SD規格環境の考察

December 15, 2019
Lost Data and SD Memory Cards: A Primer

By: Paul Norbury, founder and chief executive of Cardwave

While small and compact, SD memory cards are extraordinarily complex devices that are at the heart of our digital world. They are used in many different devices and applications including wireless communications, digital imaging and networking. Amazing technology, given their small footprint and the massive amount of storage SD memory cards can now provide. Critical to using SD memory cards is knowing how to maintain strong data integrity, understanding what can create potential data loss and how to avoid it.

Why do SD memory cards lose data and what are the causes?

SD memory cards typically lose data due to user or card error. User error can occur because many people don’t understand that SD memory cards continue to write data to the memory location for a period of time after the user has finished what they’re doing. The most common example is when the user tries to eject the card prematurely from the host device while the card or device are still in a write-state. Users who are not aware of this standard device behavior have a higher risk of failure. Although some devices have flashing lights or a screen to warn the user that the card is still in a write-state, many don’t.

Data loss can also occur from a failure in the card itself. There are many contributing factors, including but not limited to:

Examples: Counterfeit SD Memory Cards Seized
  • A failure in the firmware to process or manage a command.
  • Loss of power or a variation in power that drops below the card’s operating specification, especially when data is being written.
  • Corruption of the file system, resulting in the loss of the navigation path to the data. The
    data still exists but can’t be accessed, so the navigation path must be reset and re-mapped. There is further risk if the file system is not performing correctly, which may result in a data misread and either erase or overwrite the needed data.
  • Contamination of the card, file system or data due to poor handling, often created when the card comes in contact with liquids.

What can users do to prevent data loss?

To prevent SD memory card data loss, users should always ensure the card has finished writing data before they eject the card. Most operating systems on personal computers give the user the option to eject or request the removal of media from the host device, but industrial and non-consumer devices don’t have this option. Therefore, it’s important to understand that it’s important to wait before ejecting the card, thereby allowing the card and device to properly complete the data transfer and writing process. This will allow safe removal of the card and prevent any corruption errors.

Users should also consider the quality of the SD memory card. There are many fake and poor quality imitations in the marketplace that are not designed or manufactured to the same high levels of quality that you expect from reputable brands available from the SD memory card market. Poor performing cards can contribute to data loss due to them being manufactured with low quality flash memory or poor engineering. Sellers of fake cards tend to use downgraded memory, write their own firmware or improperly use another company’s IP.

SD is the industry standard and it’s utilized across multiple market segments of the portable storage industry. Many companies work collaboratively to ensure the SD standards are maintained and properly built into the technology. Because some companies choose to ignore these standards and do not follow SD specifications, their cards may not work properly and ultimately fail, creating unnecessary stress for the user and a potential loss of data.

Whether you are a consumer or a business using SD memory cards, there is a value in being able to confidently rely on the data you need to capture. From saving an important memory to running an operating system – users should be able to confidently and consistently capture and store data using their quality SD memory card. When this process fails, resulting in the loss or corruption of data, it can be far more devastating than being simply frustrating. While no one should ever guarantee this will never happen, the choices users make about what to buy, where to buy and how to use SD memory cards will contribute to creating a positive experience and relationship with our valuable data.

What is the principle behind data recovery?

The principle behind data recovery is to find where a file is corrupt or where the file system misreads its location and copy the file/data to a new location. File headers and parts of files can be rebuilt from other files, effectively transplanting good data over corrupt data. Corrupt data is essentially a foreign language to the controller on the card, but it is still data (i.e., ones and zeros), so erasing it and replacing it with good data means the controller can understand the language. Data recovery software can manage most of these services, but like SD memory cards, there are different options – and you can’t believe everything you read.

What can users do if they need a recovery service?

Users who need recovery services can often download software and perform the recovery themselves. This is a significant change from the early generations of SD memory cards (2002-2008), when cards were shipped to a skilled technician for data recovery. The internet is excellent for researching service options and there are many great providers, but there are also bad providers and bad software. For the non-techies, most reputable and well-known stores offer a recovery service for people who are not as confident about software downloading and installation. Using a third-party provider may still require that the SD memory card be sent to a specialist.

In recent years the industry has seen data recovery services commoditized, which has both advantages and disadvantages. The advantages are that the services are more readily available and affordable. The disadvantages are that some people and organizations have not made the same investments to provide a quality service.

Most trusted manufacturers of quality SD memory cards now include offers to trial their data recovery software with the purchase of a high-end card. Many buyers view this offer as added value and it is therefore a positive for them, but it can also be seen as a negative because it implies that data recovery may be required at some point. It should be considered a good value and practice to have access to safeguards without having to pay and additional premium, especially when the software is from a quality manufacturer or a service provider endorsed by that manufacturer.

With online services, users can easily download a software tool and quickly understand whether or not they can recover their lost data. In most cases, the user will need to purchase a license to operate the recovery software, which is typically valid for at least 12 months.

The negative side of this is that there are some companies that advertise free data recovery. However, nothing is free. These companies entice consumers with offers of a free recovery, but they don’t always make clear that the offer applies only for the first 1MB or 1GB of data. The cost of recovering large amounts of files or data can be significantly more expensive than buying an annual license or using a different service, so it is always a good idea to check the total cost before you buy.

Where organizations or individuals have a more serious problem, skilled technicians can recover data directly from the flash memory. The only way to provide this service is to bypass the flash memory controller and talk directly to the flash memory in an electrostatically safe environment, which requires a variety of testing and measurement equipment and prior knowledge of the controller’s vendor commands. This can be expensive, but industry sectors like law enforcement, the judiciary and other data centric industries are prepared to pay for this level of support because of the value of the data they need to recover.

In summary, there are service providers and tools available that will help most people in the unfortunate event of a data loss or not being able to recover data and files from an SD memory card. Another option are data recovery specialists that have many years of expertise and knowledge, plus the tools and equipment needed to provide a high-level service. Most data is important for a variety of reasons, and its value can sometimes be priceless – but should the worst happen, there are positive and reliable solutions available.

Paul Norbury is the Founder and CEO of Cardwave. He can be reached at paul.norbury@cardwave.com.

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