RPi Overlay file system?

Eric Gammeter

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Oct 5, 2021, 8:33:38 AM10/5/21

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Any information about using the RaspberryPi Overlay Filesystem to facilitate lower read/writes to the SD card? I have lost one SD card so far- granted that was over a 2-year period of running WEEWX. Just curious.

vince

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Oct 5, 2021, 11:07:02 AM10/5/21

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On Tuesday, October 5, 2021 at 5:33:38 AM UTC-7 n8a...@gmail.com wrote:

Any information about using the RaspberryPi Overlay Filesystem to facilitate lower read/writes to the SD card? I have lost one SD card so far- granted that was over a 2-year period of running WEEWX. Just curious.

You'll need your syslog(s), and the archive and public_html trees someplace weewx can write to.

You can get most of the way there in alternate ways by setting up a tmpfs and writing the most chattery things there. I do this on my model-B pi which 'do' have occasional SD failures.

#---- /etc/fstab snippet ---

#---- put logs and tmp dirs in ramdisk ---

tmpfs /tmp tmpfs defaults,nosuid,mode=0755,nodev,noatime 0 0

tmpfs /var/log tmpfs defaults,nosuid,mode=0755,nodev,noatime 0 0

tmpfs /var/tmp tmpfs defaults,nosuid,mode=0755,nodev,noatime 0 0

Eric Gammeter

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Oct 5, 2021, 4:21:36 PM10/5/21

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OK Vince- sounds like a plan. Do they eventually get written to perm storage? Perhaps during a reboot?

vince

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Oct 5, 2021, 4:52:48 PM10/5/21

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Unsure what you are asking, but if you choose to put things into tmpfs or ramdisk then 'you' have to do something manually to copy any such data out to physical read-write media somehow. In a past $job I did this with a cron job that mounted a partition, copied the file out, then unmounted the partition. That didn't eliminate issues, but it minimized the risk of taking a power hit at the wrong time.

That said, you really don't have to do this with a pi3/3+/4 and a good SD card unless you really want to. My pi3 and later have never corrupted a SD card.

Eric Gammeter

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Oct 6, 2021, 3:55:52 PM10/6/21

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That's good- that you have never had an SD card go south. I have tested out the file overlay process for a day or 2 now- and things are operating normally- as far as I can se...that is: I don't see any errors in the syslog with debug=1. Thanks for your input.