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Best way to keep a hot spare SD card for a raspberry pi? (self.selfhosted)

submitted 3 months ago by traches 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 (2 children)

Why are you using a MicroSD at all? Get a used minipc with two sata ssds or a single board computer with eMMC or mpcie support

[–] [email protected] 6 points 3 months ago

Get a used minipc

Why, when the Pi is working fine? Just get a USB to SATA cable. This one works great with the Pi: https://a.co/d/8Jv2Erj

[–] traches 4 points 3 months ago (1 children)

Yeah, I definitely won’t be buying a new pi anytime soon for exactly that reason but I’ve had this one for awhile and would prefer to do something useful with it.

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

BTW in my anecdata I've yet to have a failure on any of my SanDisk Extreme Pro SD cards. I have 4 in active use on different Pi 4s. The oldest one is in use since 2018-ish. It used to be a NAS till 2022 so roughly 3-4 years of 24/7 use with a bog-standard OS. It's now running OpenWrt which does fewer writes.