I have set up SD card mirroring using openhabian menu 53, and confirmed that the timers it created are running using systemctl list-timers:
openhabian@openhab:~ $ systemctl list-timers
NEXT LEFT LAST PASSED UNIT ACTIVATES
Sun 2022-01-09 18:49:04 MST 1h 32min left Sat 2022-01-08 18:49:04 MST 22h ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.service
Mon 2022-01-10 00:00:00 MST 6h left Sun 2022-01-09 00:00:14 MST 17h ago logrotate.timer logrotate.service
Mon 2022-01-10 00:00:00 MST 6h left Sun 2022-01-09 00:00:14 MST 17h ago man-db.timer man-db.service
Mon 2022-01-10 00:08:04 MST 6h left Sun 2022-01-09 11:09:49 MST 6h ago apt-daily.timer apt-daily.service
Mon 2022-01-10 02:02:35 MST 8h left Sun 2022-01-09 02:00:49 MST 15h ago sdrsync.timer sdrsync.service
Mon 2022-01-10 06:58:34 MST 13h left Sun 2022-01-09 06:44:49 MST 10h ago apt-daily-upgrade.timer apt-daily-upgrade.service
Fri 2022-07-01 01:15:00 MDT 5 months 20 days left Sat 2022-01-01 01:15:44 MST 1 weeks 1 days ago sdrawcopy.timer sdrawcopy.service
I read in the documentation that if the internal SD card fails, I should “replace the broken SD card in the internal slot with your backup card from the external reader. Get another SD card that matches the size of the backup (now in internal slot) card and use menu option 54 to copy your active backup card back to the new one.”
I currently have a 16 GB SD card in the internal slot and a 128 GB SD card in an external SD card reader in one of the USB ports of the Pi. My expectation was that if the 16 GB SD card failed, I would replace it with a card the same size. But this sounds like I would need a second 128 GB card and going forward I would need them both even though the recommended hardware is a 16 GB card.
Also, I’m a little unclear on how using the mirrored card backups actually works. How can it boot using the mirrored card that has an old full back up and a recent incremental back up? I would think I would need to do something to create the latest complete set from these two.
As I said, I haven’t had trouble yet, I’m just trying to be prepared for when I do. Thanks in advance for any insights and help.
The application isn’t designed to create backups of backup.
So should you be in need (already running off the 128G backup) either get another 128G
or restore your backup to a new 16G or reinstall from scratch there and import your config.
I don’t know what exactly will happen but you can also try this: run off the 128G card, insert another 16G as the backup and use menu 54.
Your 128G backup card first 2 partitions should match those of your internal 16G card, the rest is in partition 3. openHABian might refuse to do anything (because it is not designed for this setup to work) or start copying at least the first 2 partitions then spit some error on the 3rd.
debugmode=maximum so you see the commands that copy the first partitions then you can also replay those manually.
Thanks for the helpful response. I better understand the mirroring function. it is exactly what it says - it mirrors the internal SD card. I performed a simple experiment and shutdown the Pi, removed the internal card, removed the USB SD card reader and put that card in the internal slot. When I powered on the Pi, everything appeared to be there and running just like it was on the original card. (I then switched back to the original internal card and replaced the back up in the USB reader).
I was trying to make it too complicated. It is as simple as it sounds, and that is a great thing.
i have a prob with auto mirroring,I set it up a month ago and today i swap the external card with the internal one.I boots up but it is not up to date, in fact i see my openhab state when i first set up mirroring one month ago.It is like its not makes fresh back ups every day.I check my timers and they seem ok.
openhabian@openhabian:~ $ systemctl list-timers
NEXT LEFT LAST PASSED UNIT ACTIVATES
Thu 2022-05-12 19:00:51 EEST 2h 30min left Thu 2022-05-12 08:30:35 EEST 8h ago apt-daily.timer apt-daily.service
Fri 2022-05-13 00:00:00 EEST 7h left Thu 2022-05-12 00:00:25 EEST 16h ago logrotate.timer logrotate.service
Fri 2022-05-13 00:00:00 EEST 7h left Thu 2022-05-12 00:00:25 EEST 16h ago man-db.timer man-db.service
Fri 2022-05-13 00:42:47 EEST 8h left Thu 2022-05-12 03:02:18 EEST 13h ago firemotd.timer firemotd.service
Fri 2022-05-13 02:01:14 EEST 9h left Thu 2022-05-12 02:08:02 EEST 14h ago sdrsync.timer sdrsync.service
Fri 2022-05-13 06:58:33 EEST 14h left Thu 2022-05-12 06:16:03 EEST 10h ago apt-daily-upgrade.timer apt-daily-upgrade.service
Fri 2022-05-13 13:04:52 EEST 20h left Thu 2022-05-12 13:04:52 EEST 3h 25min ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.service
Sun 2022-05-15 03:10:09 EEST 2 days left Sun 2022-05-08 03:10:18 EEST 4 days ago e2scrub_all.timer e2scrub_all.service
Mon 2022-05-16 00:44:04 EEST 3 days left Mon 2022-05-09 00:41:35 EEST 3 days ago fstrim.timer fstrim.service
Fri 2022-07-01 01:15:00 EEST 1 months 18 days left Mon 2022-04-04 16:48:31 EEST 1 months 7 days ago sdrawcopy.timer sdrawcopy.service
Manually run the service or the script that the sync timer executes, see