Syncthing on older smartphones as redundant backup devices - recommended?

I got several devices running Syncthing syncing a folder and you can never have too many backups if things go wrong. I am deciding whether it would be a good idea to add an “old unemployed” 64 GB Samsung Edge 6+ (released 2015) into the group. It will become a stationary plugged-in-all-the-time Syncthing device.

But here’s a concern: The Edge 6+ has been used for 3 years and never got used again up until now. I brought it back to life, factory reset it and such. All seems to be ok, but I am concerned about aging hardware failure which could corrupt the files. So here’s the question:

  1. In this scenario, will there be any possibility that somehow bits and bytes of a file got corrupted and then got sync to other devices?

  2. Actually, is it recommended to use old smartphones for something like this?

You should be able to utilise old phones like that no problem. Please keep in mind though that Syncthing itself isn’t meant for backup per se. It does provide redundancy though, and with file versioning enabled, you can use it for simple backup purposes too.

If you worry about data corruption, you can just set all folders to Receive Only. I’d also enable (staggered) file versioning.

I personally think old phones can actually be great for this purpose, as they usually use very little energy. Just make sure you’ve got enough storage, and also that Syncthing won’t be killed by the OS when running in background (see

I am too new at syncthing to comment on useage, but I bought a new (old stock) Pixel 1 to do exactly this - to be a WiFi only backup hub, shuffling files between my Pixel 3 phone and SLR camera up to Google Photos and/or Google Drive.

If your older phone’s battery is not user-replaceable, you may want to check out “Chargie”, a USB dongle that allows one to limit the recharging of one’s battery to 90% or whatever, which greatly prolongs the service life of the battery. (Not recharging the battery to 100% results in longer life, or so they say…)

I am not sure how to handle the problem of limited memory in older phones, but my expectation is to not have more photos in any one day than I can handle with the old phone. My hope of having all this happen “while I sleep” means getting a much better understanding of both syncthing, and Google Photos “backup” and “cleanup” processes, as it seems that I cannot force things, but must wait for each to take their time, and finish. Still don’t understand how to simply count and compare on anything other than total size of total files, as there are no file counters in Google Photos that do more than say “about x files”.

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