How do you investigate high load average on a Linux server?
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Quick Answer
Correlate load with CPU (top/mpstat), run-queue and I/O wait; high load with high iowait points to disk, high with %us to CPU.
Detailed Answer
Load average counts running + uninterruptible (D-state, usually I/O) processes. Use top/htop for per-process CPU, vmstat/mpstat for run queue and iowait, and iostat for disk. High load with low CPU and high iowait means storage is the bottleneck, not CPU — a common misdiagnosis.
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Interview Tip
Load includes D-state I/O waiters, not just CPU — key nuance.
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