SD Card mirroring - SD Card size mismatch


I am running OH4 on a PI3. Trying to set up SD card mirroring, I am using a 64 SD Card for
Openhab, so I bought a USB sd card reader and several 64 SD cards. WIth a new SD card inserted in my USB sd card reader, lsblk on my PI3 is now showing this:


This error I am getting looks like this

Its true, the new 64 SD card seems to be a little bit smaller (?)
Im bumped out now, I thought I am OK buying any SD card, same size or bigger.

Maybe I am just missing to format the new SD card in my USB reader? How/Can I format the new SD card in my USB reader (?)

Thank you!

Well, the documentation mentions this explicitly:

So your backup SD card should be larger than the system SD card to avoid this. I would not try fiddling with your SD card to enlarge it

Well it should do if the mirror SD is at least as large as the original one.
When it’s not you should change cards. Reinstall your box on the smallest of your SDs.
It’s simple. Export your config and use this feature to reimport it.

Well I thought if I get me some 64 SD cards that are the same card size I have running in the PI, all good and everyone is happy.

Unfortunality not, and I do not understand why my new sd card has 0.5 Gbyte less than the one in the PI (?)

Should I have installed plain OH4 onto my external SD cards via Etcher first, and then the openhabian sd mirroring would recognize the external SD as sort of the same size ?

you can enable debugmode=maximum then you’ll see what it’s doing. and how large the cards really are.

I don’t understand that question. Just proceed as I suggested.