Explanation of microSD card classes and speeds

[stricknook]

NC button(not as not above...)

the NC getting opened up has made android/google golden(fine,opinion) is a shortcut button and or a tab too much? just because theres info to be found here dosent mean we are not made to dig past the phone stuff first.
and is this more of a stich and bitc#$ site or more or less tech. than xda?

 

[jmunchies1]

Here's a 32GB San Disk card I picked up off Amazon, the bulk one. No class label.


-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
Crystal Dew World : Crystal Dew World
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read : 10.555 MB/s
Sequential Write : 6.210 MB/s
Random Read 512KB : 10.409 MB/s
Random Write 512KB : 6.692 MB/s
Random Read 4KB (QD=1) : 1.032 MB/s [ 252.0 IOPS]
Random Write 4KB (QD=1) : 2.545 MB/s [ 621.4 IOPS]
Random Read 4KB (QD=32) : 0.719 MB/s [ 175.5 IOPS]
Random Write 4KB (QD=32) : 2.674 MB/s [ 652.8 IOPS]

Test : 50 MB [D: 0.0% (0.0/29.7 GB)] (x5)
Date : 2011/04/09 15:49:07
OS : Windows 7 SP1 [6.1 Build 7601] (x64)



I actually don't have my Nook yet, it's coming soon, but I'm pretty disappointed with those numbers. I plan on install a rom to the internal memory, but even for copying files to the card for storage seems like it's going to be really slow.

Anybody have any 32GB card recommendations?

 

[denshigomi]

I keep seeing people misunderstanding what the class rankings of microSD cards are and mean.
...
Class 2: read/write at 16Mbits/second (~1.9 MB/second).
Class 4: read/write 32 Mbits/second (~3.9 MB/sec).
Class 6: read/write 48Mbits/second (~5.7 MB/sec).
Class 10: read/write 160 Mbits/second (~19 MB/sec).

This is wrong.

The class number represents the minimum guaranteed sustained data transfer rate of the card in megabytes per second. Very simple.

Class 2 = 2 megabytes per second.
Class 4 = 4 megabytes per second.
Class 6 = 6 megabytes per second.
Class 10 = 10 megabytes per second.

No knowledge of bits versus bytes is needed.

Your megabytes per second values are all incorrect.
And for class 10, both your bit and byte values are wildly incorrect.