CompTIA Linux+ XK0-006 (V8) Practice Question

The combination of a high I/O wait (%wa) with a high load average indicates that processes are waiting on storage, not the CPU. This is confirmed by the iostat output, where %util near 100% and a very large avgqu-sz (average queue size) show that the storage device is saturated. On older Linux systems, the default I/O scheduler was often CFQ (Completely Fair Queuing), which is optimized for spinning disks and can add unnecessary overhead on fast SSDs. Modern schedulers like mq-deadline or none are better suited for solid-state storage. They remove complex re-ordering logic, shortening the path through the kernel block layer, which can significantly reduce I/O wait time and improve responsiveness.

The other options do not target the storage bottleneck: increasing swappiness would generate more disk I/O, worsening the issue; lowering PostgreSQL's shared_buffers reduces its memory cache, forcing more disk reads; and disabling network offloading affects NIC processing, not disk latency. Therefore, changing the I/O scheduler is the most effective remediation in this scenario.