How to check IO Wait on a SolusVM server?

Question

How to check IO Wait on a SolusVM node and find which VM is causing high disk I/O?

Answer

1. Check the overall IO Wait on the node. The wa value in the CPU line shows the percentage of time the CPU spends waiting for disk I/O:

   # top

   or

   # vmstat 1 5

2. Check CPU and memory usage per VM:

   # virt-top

3. Find the VM that generates high disk I/O. The -o option shows only processes that are actively doing I/O:

   # iotop -o

Each VM runs as a qemu process. Match the process to a VM by its name or PID, for example:

# ps -p <PID> -o args | grep -o "guest=[^,]*"

Note: If virt-top or iotop is missing, install it:
- AlmaLinux/Rocky/CentOS: # yum install virt-top iotop
- Debian/Ubuntu: # apt install virt-top iotop

Run the commands as root on the compute node, not inside the VM.