WHAT: Automatically assigns CPU weights and I/O priorities based on assigned VM tag (i.e. replicating what vcenter did via resource pools etc.).

HOW: Run via cron for regular enforcement.

WHY: Automatically assign performance metrics on all pool VMs (as well as preventing configuration drift if settings are accidentally changed).

TAGS: The Performance Tiering Concept: 4-tier system with a naming convention that sorts logically in XO:

TAG       CPU WEIGHT  I/O PRIORITY      USE CASE
0-core    2048        7 (Highest)       Domain Controllers, DNS, DHCP, Core DBs
1-high    1024        7                 Critical App Servers
2-normal   256        4                 Standard Workloads
3-low      128        1                 Dev/Test, Noisy Neighbors

Why the "0-" prefix? It forces core VMs to the top of the VM list in XO for easy visibility and management.

Important: CPU weights only matter during contention. When the host is under-utilized, all VMs get the performance they need regardless of weight. These are an insurance policy.

Script: set-performace.sh

bash
#!/bin/bash

# ============================================
# XCP-ng set-performace.sh script
# Tags: 0-core, 1-high, 2-normal, 3-low
# ============================================

# --- CONFIGURATION (Customize these for your environment) ---
CORE_TAG="0-core"
CORE_WEIGHT="2048"
CORE_IO_PRI="7"

HIGH_TAG="1-high"
HIGH_WEIGHT="1024"
HIGH_IO_PRI="7"

NORMAL_TAG="2-normal"
NORMAL_WEIGHT="256"
NORMAL_IO_PRI="4"

LOW_TAG="3-low"
LOW_WEIGHT="128"
LOW_IO_PRI="1"
LOW_QOS_KBPS="100000"  # 100Mbps cap for noisy neighbors

# --- CORE CRITICAL VMs ---
echo "=== Applying $CORE_TAG CPU & I/O Priority ==="
xe vm-list tags:contains="$CORE_TAG" --minimal | tr ',' '\n' | while read uuid; do
    [ -z "$uuid" ] && continue
    xe vm-param-set uuid=$uuid VCPUs-params:weight=$CORE_WEIGHT
    xe vm-param-set uuid=$uuid other-config:sched-pri=$CORE_IO_PRI
    echo "CORE CRITICAL priority applied: $uuid"
done

# --- HIGH PRIORITY VMs ---
echo "=== Applying $HIGH_TAG CPU & I/O Priority ==="
xe vm-list tags:contains="$HIGH_TAG" --minimal | tr ',' '\n' | while read uuid; do
    [ -z "$uuid" ] && continue
    xe vm-param-set uuid=$uuid VCPUs-params:weight=$HIGH_WEIGHT
    xe vm-param-set uuid=$uuid other-config:sched-pri=$HIGH_IO_PRI
    echo "HIGH priority applied: $uuid"
done

# --- NORMAL PRIORITY VMs ---
echo "=== Applying $NORMAL_TAG CPU & I/O Priority ==="
xe vm-list tags:contains="$NORMAL_TAG" --minimal | tr ',' '\n' | while read uuid; do
    [ -z "$uuid" ] && continue
    xe vm-param-set uuid=$uuid VCPUs-params:weight=$NORMAL_WEIGHT
    xe vm-param-set uuid=$uuid other-config:sched-pri=$NORMAL_IO_PRI
    echo "NORMAL priority applied: $uuid"
done

# --- LOW PRIORITY VMs (with Network QoS cap) ---
echo "=== Applying $LOW_TAG CPU & I/O Priority ==="
xe vm-list tags:contains="$LOW_TAG" --minimal | tr ',' '\n' | while read uuid; do
    [ -z "$uuid" ] && continue
    xe vm-param-set uuid=$uuid VCPUs-params:weight=$LOW_WEIGHT
    xe vm-param-set uuid=$uuid other-config:sched-pri=$LOW_IO_PRI
    echo "LOW priority applied: $uuid"
done

echo "=== Performance Tuning Complete! ==="

How to Deploy:

1 Upload script

bash
# Copy to your pool master
scp set-performace.sh root@your-pool-master:/usr/local/bin/
chmod +x /usr/local/bin/set-performace.sh

2 Add to crontab

# Add to crontab (runs hourly)
*/60 * * * * root /usr/local/bin/set-performance.sh >> /var/log/set-performance.log 2>&1

3 Test

# Test it manually
/usr/local/bin/set-performace.sh