MicroSD Card performance variance on XO-1.5

[Martin Langhoff]

We recently saw that (at least some) XO-1.5 developer machines (C1,
"ramp" units, etc) have SD cards that are significantly faster than
what is being shipped to end users.

This was a surprise to me (and probably to a few more of us) -- we
assumed that most dev machines had a similarly spec'ed SD card to the
shipping machines. AIUI, we intended to have an assortment of
"candidate" SD cards on the ramp units, the units I've seen all have
pretty fast cards :-)

This probably explains the scattered results of testing Record
audio/video sync -- with lots of 'works for me' vs "definitely doesn't
work". The slower SD cards are significantly slower.

Deployments can request faster cards (at a cost), but I think it makes
sense to test with the lowest common denominator. And we definitely
need to understand what SD card is behind each "works" or "doesn't"
report re Record and other write-intensive tasks.

To aid clarity, Mitch has added a ".speed" test to OFW -- and we've
timed a few cards with it:
http://wiki.laptop.org/go/SD_and_USB_FLASH_Drive_Performance

How to check your internal SD card brand & model:
http://wiki.laptop.org/go/XO_Debugging_tips

cheers,



m
-- 
 martin.langhoff at gmail.com
 martin at laptop.org -- School Server Architect
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