The SANDISK SD Card Slowdown

Are you talking about how capacities aren’t growing as quickly as they did in the past?

No but the rate of doubling capacity (from 2009:   that existed until we reached 16gb or so needed to stop if only due to the reason that most people with media players don’t use up that amount of space (especially since the advent of cloud based players such as Spotify and Google music) and photographers shouldn’t carry all of their photos in a single high capacity storage card that could easily be swallowed/lost or fail.

I am talking about the apparent slowdown in new high capacity micro SD card read/write rates, in reality this is just an evaluation of the r/w rates of SD cards over the past 5 years.

That is a big claim… is there proof?

Yes! I recently bought a HTC HD2 and promptly installed both WP7 and Android on it,  these are 2 operating systems which shine on the HD2 when given fast storage cards so I had to evaluate suitability of cards that I purchased throughout the years (these aren’t cherry picked ‘review samples’ provided by manufacturers)  including a new 16GB ‘class 6’ SanDisk card.

What cards were tested?

These were all Micro SD cards, the majority of which were made by SanDisk

  1. 16GB SanDisk Mobile Ultra, Class 6, 2012
  2. 2GB SanDisk, Class 2, 2010 (pack in with new phone)
  3. 6GB SanDisk, Class 4, Mid 2008 (Killed in Action)
  4. 2GB Verbatim,  Mid 2008
  5. 4GB SanDisk, Class 2,  Nov  2007


Not Pictured: The Verbatim 2GB card that was used to take this image

All of these cards are genuine and were bought from respected retail chains.

How were these tested?

The cards were formatted using FAT 32 with default cluster settings using the windows formatter tool, they were then tested using CrystalDiskMark (sequential) and H2Testw (used to detect counterfeit flash memory products) both with a 500mb file size.

These tests were run on 2 different computers one desktop using a Belkin USB card Reader (2011) and one Laptop which with an inbuilt card reader, both  benchmarks were run twice on both computers and averaged (the raw numbers are in the attached spread sheet ).



Testing Outcome



The results show the following ranking by performance (fastest first):

  1. 2008 SanDisk 6GB
  2. 2007 SanDisk 4GB
  3. 2008 Verbatim 2GB
  4. 2012 SanDisk 16GB
  5. 2010 SanDisk 2GB

So it seems that these cards ARE getting slower this could be due to many reasons but I think either the newer Classification system (Class 6 etc) means that card manufacturers can develop cards which support the bare minimum speeds required to satisfy a speed rating or that this performance reduction was to provide more reliable operation of the cards.

On a side note the 6GB SD card died during this testing, it is no longer being recognised in ANY device not even in some E series Nokia phones that seem to be able to resurrect some locked cards from the grave. Was this due to a high performance interface that was unreliable or simple fatigue? I will likely never know.

In the end I used the 16Gb card on my HD2 as holding more than 3 albums held too much appeal.

The raw data can be accessed in a Google spread sheet at :

UPDATE: It appears to be a SanDisk problem, other people have noted and recorded similar speed drops