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Thread: Dump1090-mutability JSON files

  1. #1
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    Dump1090-mutability JSON files

    I have recently switched from using windows to a Raspberry Pi 3B+. Although I am no stranger to LINUX/UNIX, I am new to the RPI but I followed the helpful guide on here about installing DUMP1090-mutabilty and FR24Feed and everything is working fine.

    I noticed that there is more activity on the SD card than I had expected as the LED flashes quite a lot. Obviously, some of this is down to the core O/S but I wondered whether there was data being written to the card that wasn't needed for my configuration.

    One thing I found was the JSON files, which are created by DUMP1090-Mutability. I wondered if these are really needed and what the implications of having them were in terms of SD Card longevity.

  2. #2
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    Those json files are being written to /run, this directory lives in the RAM, not on the sd-card.

    If you have the quite useful logging enabled in fr24, you can disable that if you want but it is not much in terms of writes.

    Other stuff like message rate graphs (for example https://github.com/wiedehopf/graphs1090#graphs1090) writes to disk quite a bit more.

    It seems most sd-cards dying in RPi was probably in the early generation RPi and not even necessarily due to write volume.
    All electronics is happier when cool, so if you have a plastic case you might consider taking a drill to it (without the pi inside).

    Anyhow if you are not worried about data loss, you can do this:
    Code:
    sudo cat >/etc/sysctl.d/07-dirty.conf <<EOF
    vm.dirty_ratio = 40
    vm.dirty_background_ratio = 30
    vm.dirty_expire_centisecs = 360000
    EOF
    This makes it so that changes to files are only actually written to disk after an hour or when the RAM is full.
    That should reduce the frequency of writes to the sd-card significantly.
    If the same file is changed multiple times in that timeframe, that also reduces how much is written to disk.
    (This is very useful if you are using a database recording statistics like the graphs do and reduces disk writes from 80 MB per hour to around 10 MB per hour).
    Last edited by wiedehopf; 2019-04-11 at 16:29.

  3. #3
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    Thanks for the info. I hadn't actually looked to see where /run is located and I guess I'm more rusty on LINUX that I realised but then it was a while back when I was working on SCO Unix and Red Hat.....

    I know that SD cards aren't expensive but these things always tend to go wrong when you least want it to happen don't they.

    I had a look at your Graphing utility and was tempted but I've been running Virtual Radar on a PC, which acts a server, ever since I started feeding to FR. I can see a lot of what is going on from that and find it particularly useful when something (A400m, Voyager, C-5m, C-130, C-17 etc.,) flies overhead and doesn't show up on FR.

    As far as drilling holes in my lovely new RPI case goes, I think I'll pass on that thanks. Good tip about removing the Pi first by the way. :->

  4. #4
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    On second thoughts...

    How wrong can a person be? I've just installed graph1090 and I'm converted. It's great, so it looks like I'll be leaving well alone.

    Thanks wiedehopf!

  5. #5
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    Sure thing

    The graphs are originally created by mutability but i added the automatic installation.

    As i said if you wan't to reduce the amount written by the graphs it's best to use the command in the box of my last post.
    Just paste it onto the console.
    While you may lose an hour of graph data in case of a power outage there's nothing else on the RPi which cares about lost data.
    (unless you use it for something else besides feeding fr24)
    there is nothing else on the

  6. #6
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    Pi is only used for Dump1090/FR24Feed

    But I was so impressed with the thing that I got a second one to play with.

  7. #7
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    I am using a Raspberry Pi and an Orange Pi since 2015. Both Pis feed data to 5 sites continously 24/7.

    I also have graphs installed since 2016, first one by J Prochazka, and now replaced by the one by wiedehopf, (because wiederhopf's graphs are lighter than JProchazka's web portal, which contain lot of other funtionality which I did not need).

    Morale of the story: Stop worrying about writes and failure of microSD card
    Last edited by abcd567; 2019-04-11 at 19:50.

  8. #8
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    I hear you abcd567.

    I had a few SD cards fail a while back and lost some stuff that wasn't saved elsewhere in time but I think they are much more robust nowadays as long as you buy good quality ones.
    Last edited by technodevotee; 2019-04-11 at 20:26.

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