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#296034 - 30/03/2007 12:08
Re: using GPS to record a trip
[Re: kilbasar]
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carpal tunnel
Registered: 13/07/2000
Posts: 4181
Loc: Cambridge, England
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Quote: According my revised calculations (this time somewhat based in reality), the NMEA data will come to about 2 megabytes per hour. Not a lot, but when you're talking about 6 weeks of driving, 32 megs won't be enough. On the other hand, assuming I go the path of making a RAM drive for temp storage, even if the RAM drive is only 1 meg in size, that means I'll only need to write to the hard drive every half hour or so (plus right before the script closes). In which case, it doesn't seem like it would be too risky to have the normal data partition set to RW for a couple of seconds every half hour. Does that make sense?
If you're prepared to do a bit of coding for it, you can eliminate remounting altogether by pre-preparing a file of large-enough size, working out which disk sectors the file occupies using ioctl(FIBMAP), and writing to those sectors directly in the partition block device. This reduces the risk of a power failure hosing your filesystem, though of course it increases the risk of a bug in your own code hosing the filesystem...
Peter
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