unraidsupertier

#!/bin/bash
# /{user script location}/btrfs-nvme-tier.sh

DATA_PATH="/data"
NVME_THRESHOLD=75  # Start tiering when NVMe hits 75% full
SSD_ADDED_FLAG="/var/lib/btrfs-ssd-added"

# Function to check NVMe space usage
get_nvme_usage() {
    btrfs filesystem usage $DATA_PATH | grep "Device allocated:" | head -2 | \
    awk '{gsub(/%/, "", $3); print $3}' | sort -n | tail -1
}

# Function to add SSDs and create tiered storage
add_ssd_tier() {
    echo "$(date): Adding SSD tier - NVMe usage at ${1}%"

    # Add SSD devices to the filesystem
    btrfs device add /dev/sda1 /data
    btrfs device add /dev/sdb1 /data

    # Convert to have mirrored SSDs as well
    # This creates a mixed topology: NVMe RAID1 + SSD RAID1
    btrfs balance start -dconvert=raid1 -mconvert=raid1 /data

    # Mark that SSDs have been added
    touch $SSD_ADDED_FLAG

    echo "$(date): SSD tier added successfully"
}

# Function to tier older data to SSDs
tier_cold_data() {
    echo "$(date): Tiering cold data to SSDs"

    # Move less-utilized chunks from NVMe to SSD
    # This preferentially moves older/fragmented data
    btrfs balance start -dusage=60,devid=1 /data &
    btrfs balance start -dusage=60,devid=2 /data &
    wait

    echo "$(date): Data tiering complete"
}

# Main logic
CURRENT_USAGE=$(get_nvme_usage)

if [ $CURRENT_USAGE -gt $NVME_THRESHOLD ]; then
    if [ ! -f $SSD_ADDED_FLAG ]; then
        # First time hitting threshold - add SSDs
        add_ssd_tier $CURRENT_USAGE
    else
        # SSDs already added - just tier data
        tier_cold_data
    fi
fi

echo "$(date): NVMe usage: ${CURRENT_USAGE}%"