Disk layout for XO-1.5

[Tiago Marques]

Hi,

On Fri, Aug 7, 2009 at 2:52 AM, Richard A. Smith<richard at laptop.org> wrote:
> Benjamin M. Schwartz wrote:
>
>> Martin Langhoff wrote:
>>>> I would urge...
>>> ...you are preaching to the ultra-converted, to the frustrated. I
>>> wasn't personally involved, but I know at least Wad & Mitch looked
>>> quite deep into this, and found no good offers. There is good evidence
>>> to trust them in hardware and low level firmware matters :-)
>>
>> Indeed; I didn't mean to suggest otherwise.  If they have written off the
>> possibility of open disk controller firmware, I am sure they have made the
>> right decision.
>
> We asked the UBFS devs if there were any devices they knew of that
> allowed raw access to the nand or otherwise tweaking of the FTL.  None
> that they knew of.  Neither Phison or SMI (The mfgs we were looking at)
> have open firmware for their FTL chips.
>
> In the end we chose to use microSDHC cards.  The B1/B2 build will have 3
> different mfg's of cards for qualification tests.  Random power failures
> are part of the qualification tests.

Cool for hardware upgrades and generally very bad for random write
speeds and consequently booting/shutting down/updating the
system/whatever. Has anyone run iometer with random read and write
patterns on the controller/sdhc?
Does the said controller do any kind of write caching to get around
the limitations of SD cards?
Or are there any microSDHC cards that I don't know of, with very good
random writes? In which I would have to get hold of some.

Best regards,

Tiago Marques

>
> --
> Richard Smith  <richard at laptop.org>
> One Laptop Per Child
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