I got an HTC Desire, a nice android phone and bundled with it I got also a Sandisk 4gb Class 2 memory. Cool, is it a real Class 2 micro SHDC? Yes, a sorta (1.9~2).
Here is a useful benchmark.
(Built-in Sandisk 4gb Class 2)
Now I see a lot of 16gb/32gb "class 6" or "class 10" micro sd memories on Ebay, with labels like Team Group, Synapse, Lexar, Topram, Kingston, Trascend, A-Data but are these really "class 6" as advertised?
I dubt, but I could be wrong. I bought a cheap "Team Group" 16gb class 6 microsd and here are the results.
(Team Group 16gb Class 6 - bought on ebay)
It perform very poorly, and I'll ask for a refund soon. It is 2.9Mb/s as write rate, so it isn't a Class 6, it shold be a Class 3 !!
Benchmarks and Tests
The are a lot of tests on internet about the read rate of this microsd or shdc memories, but the most important parameter to check is write rate! (See SDCard Organization FAQ)
A very used utility on Android is SD Card Speed Tester, honestly I don't trust on it much because everytime it gives different values. The first run I got Class 6, the second Class 2 and then Class 2 or 3. Probably it depends in which zone it writes the 300Mb for test.
An Effective test built-in with Ubuntu Linux
Running this test on a wiped memory (without partition table) I'm able to visualize some useful data about the real quality of the microsd and it won't change much the second run.
Step 1: Wipe and delete completly the memory
sudo dd if=/dev/zero of=/dev/sdb
Where "sdb" is the device of your test memory (see dmesg)
Step 2: Run the read + write benchmark
Please share your tests about the microsd you buy on internet or ebay!! And report reliable tests, a lot of people will benefit of it.