iotop shows which process is burning the disks
A disk that spikes with no obvious writer is hard to chase; iotop maps throughput straight back to the task doing the damage. System-wide tools show the symptom — high await, saturated utilization — but never the suspect: fifty processes share the disk and the average blames all of them equally. The question that ends the investigation is always per-process — who, how much, since when — and iotop answers exactly that, live, from kernel counters no application can hide from. ...