CompTIA Server+ (SK0-005)TroubleshootingMedium
A server administrator discovers that a database server is performing very slowly, and applications connecting to it are frequently timing out. Upon checking the server's resource monitor, the disk I/O utilization is consistently at 100%, even during periods of low activity, while CPU and memory usage are normal. The server uses a RAID 5 array with five 1TB drives. Which of the following is the MOST likely cause of the performance issue?
- ANetwork bottleneck to the database server.
- BA failed drive in the RAID 5 array.
- CInsufficient RAM allocated to the database.
- DExcessive CPU context switching.
Show answer & explanationAnswer & explanation
Correct answer: B. A failed drive in the RAID 5 array.
High disk I/O utilization (100%) with normal CPU and memory usage, especially on a RAID 5 array, is a strong indicator of a degraded array due to a failed drive. While RAID 5 can tolerate one drive failure, performance significantly degrades as the controller must reconstruct data on the fly.
Why the other options are wrong
- A. A network bottleneck would show high network utilization or dropped packets, not 100% disk I/O on the server itself.
- C. Insufficient RAM would likely lead to high memory usage or excessive swapping, not 100% disk I/O with normal memory.
- D. Excessive CPU context switching would manifest as high CPU usage, not primarily 100% disk I/O with normal CPU.
RAID 5 Degraded Performance
When a drive fails in a RAID 5 array, the array enters a degraded state, continuing to function but with significantly reduced performance due to on-the-fly data reconstruction.
- RAID 5 can tolerate a single drive failure.
- Performance degrades substantially when in a degraded state.
- High disk I/O with normal CPU/memory often points to degraded RAID.
Memory trick: When the disk is maxed but CPU is chill, suspect a degraded RAID making it ill.