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

submitted 4 months ago by [email protected] to c/selfhosted

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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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[–] Mellow12 6 points 4 months ago* (last edited 4 months ago) (2 children)

I’ve had very bad luck with raspberry Pi’s and SDCards. They just don’t seem to last very long. I swapped to usb storage and things got somewhat better. I just had a usb drive die after 3 to 4 years of use. When I was still using SD it seemed like multiple times a year. Heat. Power loss, you can only punch holes in silicon so many times before it wears out. Whatever the reason.

My approach for this is configuration backup not the entire os. I think this approach is better for when it’s time to upgrade the os or migrate to a new system.

For my basic Pi running WireGuard and DNS, I keep an archive of documentation on steps to reconfigure the system after a total loss. Static configs are backed up once, and If there are critical configuration items that change then I back those up weekly. I’ve got two systems (media related servers, not Pi’s) that I keep ansible playbooks to configure 90% of the system from scratch so it’s as hands off as it can be.

[–] [email protected] 2 points 4 months ago

If you are killing SD cards you shouldn't be using a raspberry pi. They aren't exactly work horses

[–] [email protected] 2 points 4 months ago

Yeah, I’m getting a pretty strong consensus here that an SSD is the way to go. I’ve also had at least one SD card die on me, and because I didn’t have backups it was pretty inconvenient. Had to recreate my homeassistant setup from scratch.

I get the config only backup, but when I have a mondohuge nas available and we’re dealing with like less than 100 gigs, why not just take a full disk image?