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iostat

Overview​

iostat reports CPU and I/O statistics for devices and partitions.

Basic Usage​

# Display basic I/O statistics
iostat

# Display extended statistics with intervals
iostat 2 5

# Show human-readable output
iostat -h

# Display statistics for specific devices
iostat -d sda sdb

Key Metrics​

  • tps: Transfers per second
  • kB_read/s: Kilobytes read per second
  • kB_wrtn/s: Kilobytes written per second
  • await: Average wait time (ms)
  • util: Device utilization percentage

Examples​

# Monitor disk utilization in real-time
watch -n 1 iostat -x 1 1

# Check for I/O bottlenecks
iostat -x 1 3 | grep -E "^Device|sd"

Performance Analysis​

  • 0-20%: Low usage, healthy
  • 20-50%: Moderate usage, normal
  • 50-80%: High usage, monitor closely
  • 80-95%: Very high usage, potential bottleneck
  • 95-100%: Disk is saturated, serious performance issues
  • vmstat - Virtual memory statistics
  • sar - System activity reporter
  • iotop - I/O monitoring tool
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