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Best way to keep a hot spare SD card for a raspberry pi? (sh.itjust.works)

submitted 3 months ago by [email protected] to c/[email protected]

54 comments fedilink hide all child comments

I have a load-bearing raspberry pi on my network - it runs a DNS server, zigbee2mqtt, unifi controller, and a restic rest server. This raspberry pi, as is tradition, boots from a microSD card. As we all know, microSD cards suck a little bit and die pretty often; I've personally had this happen not all that long ago.

I'd like to keep a reasonably up-to-date hot spare ready, so when it does give up the ghost I can just swap them out and move on with my life. I can think of a few ways to accomplish this, but I'm not really sure what's the best:

The simplest is probably cron + dd, but I'm worried about filesystem corruption from imaging a running system and could this also wear out the spare card?
recreate partition structure, create an fstab with new UUIDs, rsync everything else. Backups are incremental and we won't get filesystem corruption, but we still aren't taking a point-in-time backup which means data files could be inconsistent with each other. (honestly unlikely with the services I'm running.)
Migrate to BTRFS or ZFS, send/receive snapshots. This would be annoying to set up because I'd need to switch the rpi's filesystem, but once done I think this might be the best option? We get incremental updates, point-in-time backups, and even rollback on the original card if I want it.

I'm thinking out loud a little bit here, but do y'all have any thoughts? I think I'm leaning towards ZFS or BTRFS.

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[–] [email protected] 0 points 3 months ago (7 children)

ZFS isn't going to perform well on a Raspberry Pi

[–] [email protected] 1 points 3 months ago (2 children)

Performance is all but irrelevant in this case

[–] [email protected] 1 points 3 months ago (1 children)

You say that but when the system starts to lock up you might change your tune

[–] [email protected] 1 points 3 months ago* (last edited 3 months ago)

Why would it lock up? ZFS will use as much RAM as you give it and it doesn't seem CPU-bound unless you turn on encryption. It's not a cluster FS like Ceph. Why do you expect ZFS to lock up and Btrfs not to?

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