On 9 Mar 2018 16:46:54 GMT, ray carter  declaimed the
following:

>On Fri, 09 Mar 2018 12:02:00 +1200, Nick Mackechnie wrote:
>
>> Hiya,
>>
>> I have a Pi I use for Flightaware, class 10 SD memory corrupts over time
>> with Flightaware (maybe to do with IO?) , a Class 4 seems to do the
>> trick. Can any one recommend a good source, I've tried buying a few, and
>> the online stores have 'upgraded me ' to Class 10 which isn't that
>> useful :-)
>>
>> Nick.
>
>Out of curiosity, are you overclocking? Is your power supply really
>adequate?

 Class 6, if found, should also be usable.

 Class 2/4/6 SD cards are rated for /fragmented/ file I/O (what one
would get on a still frame camera with picture deletions).

 Class 10 SD cards are based upon /streaming/ file I/O (as would result
from video recording), and that is on a freshly formatted card.

 Cheaper C-10 cards may only maintain 2 "open allocation units" -- one
for the streaming data, and one for the "directory". Writing multiple files
in parallel (system log, user data, what have you) requires such a card to
close an allocation unit, obtain a free one and open it, copy anything from
the front of the modified file and free that older allocation unit for
reuse, then write new data... Better cards will allow for 4-6 open
allocation units, which means interleaved file writing doesn't trigger
allocation unit swapping.


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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