ext2/3/4 group size

[Arnd Bergmann]

On Thursday 31 March 2011, Yioryos Asprobounitis wrote:
> I have a very good 2-year old 4GB class 6 Transcend 
> a poor 1-year old 4BG class 6 Kingsoton
> and  terrible 2-year old 8GB A-data
> Rating is based on iozone data and "terrible" means that I get file corruption
> quite often. Kingston is just slow.
> None of them is formatted as suggested.

If you get file corruption, the card is at the end of its life, you should
probably toss it out. I would be interested in seeing flashbench results
for this card before you throw it away. I can tell you how to do it
if you are interested.

The Kingston card probably uses a toshiba controller (oemid 0x544d in
/sys/block/mmcblk0/device/oemid), which is not suitable for ext3 at
all. The reason for the slow speed is that you have a giant write
amplification, which ages your card very quickly, and it will probably
die next unless you use it in a digital camera with FAT32, where it
can still enjoy a long and happy life as a fast card.

The transcend cards I've seen typically use samsung controllers (oemid
0x534d), which are reasonable. If you want to make measurements comparing
different file system settings, I think it only makes sense using this card.

	Arnd