Fwd: The XO-1.5 software plan.

NoiseEHC NoiseEHC at freemail.hu
Sat May 16 15:14:44 EDT 2009

> 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 
> <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... :)

Are there any plans using UBIFS?

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