Hi
On 11/07/11 22:07, Arnd Bergmann wrote:
From these numbers, it's definitely clear that there is no factor 3 in it, the erase block size has to be either 4MB or 8MB.
great.
Since you asked about the alignment in the other thread: What is the alignment of this partition? Do the numbers change if you align the block to an odd number of 4MB blocks (counting from the start of the card)?
This card is aligned to 4MB blocks (the other card was not)
Still, this could be anything. Bonnie is a high-level benchmark, so this could all just mean that MacOS is doing internal write-caching for SD cards while Linux does less of that.
What would be really interesting is to use flashbench on macos, if you can get that to build and macos supports O_DIRECT.
we will try that.
Ok. The numbers I'm usually interested in are:
- erase block size (smaller is better, lower than 4MB is hard to find on 4GB+ cards)
ok, using -a and so on
The very easy smoke test is
flashbench --open-au --open-au-nr=5 --blocksize=2048 --random
Look at how the numbers go down. Ideally, they should stay at multiple MB/s all the way down to the 16KB row, or lower. If they behave like the Kingston card you tested earlier, they are completely useless for Linux.
ok, prepare for a bunch of results :)
peter