On Sun, 25 Jan 2009, Gregory Stark wrote:
david@xxxxxxx writes:
they currently have it do a backup immediatly on power loss (which is a safe
choice as the contents won't be changing without power), but it then powers off
(which is not good for startup time afterwords)
So if you have a situation where it's power cycling rapidly each iteration
drains the battery of the time it takes to save the state but only charges it
for the time the power is on. I wonder how many iterations that gives you.
good question.
assuming that it's smart enough to not start a save if it didn't finish
doing a restore, and going from the timings in the article (~20 min save,
~15 min load and 4 hour battery life)
you would get ~12 cycles from the initial battery
plus whatever you could get from the battery charging (~3 hours during the
initial battery time)
if the battery could be fully charged in 3 hours it could keep doing this
indefinantly.
if it takes 6 hours it would get a half charge, so 12+6+3+1=22 cycles
but even the initial 12 cycles is long enough that you should probably be
taking action by then.
in most situations you are going to have a UPS on your system anyway, and
it will have the same type of problem (but usually with _much_ less than 4
hours worth of operation to start with)
so while you could loose data from intermittent power, I think you would
be far more likely to loose data due to a defective battery or the CF card
not being fully seated or something like that.
David Lang
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