When building a low-power always-on backup server, we need to prioritize:

• Idle power consumption <15W (target 5-10W)
• Linux-based OS for headless operation
• SMB/NFS protocol support for cross-platform access
• Automatic sleep/wake scheduling

Option 1: ARM-based Single Board Computer

# Raspberry Pi 4 Model B specs
- CPU: Broadcom BCM2711 (4× Cortex-A72 @ 1.5GHz)
- RAM: 2GB/4GB/8GB options
- Storage: MicroSD + USB 3.0 for HDD
- Power: 3W idle, 6W under load
- Cost: $35-$75

Option 2: x86 Low-Power Mini PC

# Intel NUC-like devices
- CPU: Celeron J4125 (TDP 10W)
- RAM: 8GB DDR4
- Storage: M.2 SSD + SATA HDD
- Power: 8W idle, 15W max
- Cost: $150-$300

For 1-4TB storage with basic redundancy:

# Sample mdadm RAID1 setup
sudo apt install mdadm
sudo mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
sudo mkfs.ext4 /dev/md0

Recommended OS: Debian minimal (no GUI) or OpenMediaVault

# Samba configuration (/etc/samba/smb.conf)
[backup]
   path = /mnt/backup
   browseable = yes
   read only = no
   guest ok = no
   valid users = backupuser

Implement wake-on-LAN for the 1-hour daily access window:

# Enable WoL in Linux
sudo apt install ethtool
sudo ethtool -s eth0 wol g

# Sample wakeup script (Windows client)
Start-Process -FilePath "wolcmd" -ArgumentList @(
    "MAC_ADDRESS",
    "192.168.1.255",
    "255.255.255.0",
    "7"
)

For very low-budget solutions, consider:

• ASUS RT-AX86U (USB 3.0 + Samba)
• GL.iNet routers with OpenWRT

# OpenWRT USB storage setup
opkg update
opkg install kmod-usb-storage block-mount kmod-fs-ext4
mount /dev/sda1 /mnt/share

For a power-conscious file server handling 1-4TB storage:

• Single-board computers: Raspberry Pi 4 (2GB RAM) with USB 3.0 HDDs (~5W idle)
• Mini-PCs: Intel NUC with Celeron J series (~10W idle)
• NAS-specific boards: Odroid-HC4 with direct SATA ports (~7W load)

# Example power measurement on Raspberry Pi:
vcgencmd measure_volts
vcgencmd measure_clock arm
cat /sys/class/thermal/thermal_zone*/temp

For basic redundancy without power penalty:

# Software RAID1 setup on Linux
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
mkfs.ext4 /dev/md0

Alternative low-power solutions:

• USB 3.0 HDDs with staggered spin-down (hdparm -S 120 /dev/sdX)
• SSDs for completely silent operation (higher $/TB)

OpenWRT-compatible routers with USB 3.0:

• TP-Link Archer C7 v2 (add external HDD)
• GL.iNet GL-MT300N-V2 (microSD storage)

# OpenWRT Samba config example
opkg update
opkg install samba36-server
vi /etc/samba/smb.conf
[backups]
   path = /mnt/usbdrive
   read only = no
   guest ok = yes

Lightweight Linux distributions:

• DietPi: Optimized for low-power devices
• OpenMediaVault: WebUI for easy management

# Automated backup script (rsync example)
rsync -avz --delete /source/folder/ user@server:/backup/folder/
echo "0 2 * * * root /usr/local/bin/backup.sh" >> /etc/crontab

# Disable unused services (Debian/Ubuntu)
systemctl disable bluetooth.service
systemctl mask avahi-daemon.service

# CPU governor setting
echo "powersave" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Monitoring tools:

• powertop (Intel)
• raspi-monitor (RPi)