[time-nuts] 5370 processor boards available

Didier Juges shalimr9 at gmail.com
Thu Feb 27 20:54:47 EST 2014


"The only time there is any exposure is during a write operation"

That is not true. By default, Linux updates the last access time for each file it reads. The last access time is stored with the file, so each file read actually causes the file to be written to as well, opening the door to all sort of mayhem is power is lost during boot. Aside the performance penalty, you can trash your drive while you were just "reading" it.

One easy optimization for embedded Linux is to turn that off. Google something like "turn off last access time"

Didier KO4BB


On February 27, 2014 9:06:31 AM CST, Brian Lloyd <brian at lloyd.com> wrote:
>The only time there is any exposure is during a write operation. When
>the
>processor board is used to run the 5370, how often is data written and
>what
>is the exposure interval?
>
>I would be willing to bet that Linux already has a power-fail NMI
>input. I
>would bet that you can find out what the worst-case PF NMI latency is
>and
>then ensure that the PS output stays up at least that long without
>having
>to worry about a battery or "super cap". (I bet PF latency is under
>1ms.)
>In that case, all you need to do is assert the PF interrupt line.
>
>Hmm, check to see if it is already there and based on nothing more than
>sagging Vcc/Vdd. I bet it is and therefore this whole discussion may be
>moot.
>
>But the idea of making the boot partition RO and the /var partition R/W
>makes a whole lot of sense to me.
>
>-- 
>Brian Lloyd, WB6RQN/J79BPL
>706 Flightline Drive
>Spring Branch, TX 78070
>brian at lloyd.com
>+1.916.877.5067
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