Fwd: The XO-1.5 software plan.

Tiago Marques tiagomnm at gmail.com
Sat May 16 18:05:59 EDT 2009

On Sat, May 16, 2009 at 8:14 PM, NoiseEHC <NoiseEHC at freemail.hu> wrote:

> Sorry, should have explained myself better, as I was also talking about
> memory speed and not size, this time.
> Ahh, if you wrote about memory size then never mind my comments. :)
> Thing is, most flash controller implementations are crap, and it will
> probably be the case with  the one in Gen 1.5. I'm quoting 0.5MB/s in *random
> writes* to the file system, nothing to do with compression. Most decent
> SSDs can write at last 1MB/s with some topping 2MB/s, in random patterns,
> sequential is about 150MB/s+. Sequential is not the problem when using SD
> cards or most USB drives, random writes is, when you're trying to have an OS
> on it.
> The best drives around, from Intel, can do 20+MB/s in random writes.
>    Most SSDs on the market are based on J-Micron controllers that can do,
> at most, 0.04MB/s in random writes. This causes the system to frequently
> stall when some app is performing heavy writes to arbitrary locations.
> Random reads are mostly very fast with every type of flash you can get.
> http://www.anandtech.com/storage/showdoc.aspx?i=3531&p=25
> 0.5MB/s in RR should be enough to avoid most stalls.
>   I hope that Mich Bradley will educate us but it seems to me that the
> hidden eraseblock handling can be the problem with those devices (and if it
> is true then compression will not help it either). It seems to be that some
> tests are required with physical hardware, a paper processor will not be
> enough... :)

True, I just thought it was a good idea to point this out before any
decisions are made, especially when most Flash vendors completely disregard
random write performance.

Best regards

> Are there any plans using UBIFS?
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