I currently have a fully functioning server with about 90TB of data, and I want to build a second server that will act as an offsite mirror/backup.

-What would be the best way to set up this second server if I want it to power on periodically (for example, once a week or once a month), sync with my main server, and then power back off?

-What software, Docker containers, or backup/sync systems would you recommend for this setup?

-Would unRAID be the best option for the second backup server, or is there another platform that might work better for this use case?

1. Powering on and off a remote server is going to require some kind of device like a KVM that can wire into the hardware or send a magic packet for Wake-On-Lan for out-of-band management.

2. I myself am in the process of setting up a self-hosted S3 API compliant container called Garage which will let me use backrest to sync my data in an S3 compatible format which im already using to send backups to backblaze b2 storage.

3. I don't see why unraid cant work. I dont see why something else cant work either.

There are 100 different ways to skin the cat.

Edited April 13Apr 13 by MowMdown

Discussion when I did a similar project 3 years ago:

On 4/11/2026 at 5:54 PM, fonzie said:

I currently have a fully functioning server with about 90TB of data, and I want to build a second server that will act as an offsite mirror/backup.

Same boat here -- ~ 50TB offsite backup server is exactly what I'm trying to figure out myself.

Don't want to run any complicated custom setups.

For the power on/off question ConnerVT's thread linked above covers it well -- WOL to wake the backup server, S3 sleep plugin to send it back to sleep when done. Works reliably without needing IPMI hardware.

For the sync software I've been looking at three options and haven't committed yet.

Syncthing is simple -- zero configuration networking, bidirectional sync, web UI only, no CLI required.

Resilio Sync is very user friendly but proprietary.

Duplicacy has better versioning and chunk-based deduplication which protects against the kind of ransomware scenario where a simple mirror would just replicate the encrypted files.

One thing worth knowing if Duplicati (not Duplicacy) comes up as a recommendation — Spaceinvaderone's tutorial on it has a disclaimer added recently noting restore reliability issues.

Worth reading before going that route.

Duplicacy is the more reliable alternative in the same general space.

Still weighing the options myself.

Would be interested to hear what others in a similar situation ended up choosing -- especially at the >50TB scale where the initial sync alone is a multi-day project regardless of what software you pick.