Root causes by 5 whys
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The 5 Whys is a problem-solving technique aimed at identifying the root cause of an issue by repeatedly asking 'why.' It emphasizes the importance of understanding the problem fully before seeking solutions, making it best suited for simple to moderately difficult problems. The method can provide valuable insights even for complex issues, as demonstrated in a troubleshooting scenario involving a virtual machine error.
Root causes by 5 whys
- 1. 5 Whys
- 2. “ไอน์สไตน์เคยพูดไว้ว่า.. ถ้าเค้ามีเวลา 1 ชั่วโมงในการแก้ไขปัญหา เค้า จะใช้เวลา 55นาที กับการมองที่ปัญหา ส่วนอีก 5นาทีที่เหลือค่อยมองถึง หนทางในการแก้ไข” “If I had an hour to solve a problem I’d spend 55 minutes thinking about the problem and 5 minutes thinking about solutions.”
- 4. 5 Whys Key Points The 5 Whys strategy is a simple, effective tool for uncovering the root of a problem. You can use it in troubleshooting, problem-solving, and quality-improvement initiatives. Start with a problem and ask why it is occurring. Make sure that your answer is grounded in fact, and then ask the question again. Continue the process until you reach the root cause of the problem, and you can identify a counter- measure that will prevent it from recurring. Bear in mind that this questioning process is best suited to simple or moderately difficult problems. Complex problems may benefit from a more detailed approach, although using 5 Whys will still give you useful insights.
- 5. Why cannot access VM on ab21345 ? 1 Because there ESXi was hang and error
- 6. Why ESXi hang? 2 Because there services Large Receive Offload (LRO) was error
- 7. Why LRO error ? Because there sub-services vmxnet3 was error 3
- 8. Why vmxnet3 error ? Because know issue (BUG) in V6.0 the interger overflow in vmxnet3 backend which leads to PSOD under certain condition. 4
- 9. Why integer overflow in vmxnet? LRO reassembles incoming network packets into larger buffers and transfers the resulting larger but fewer packets to the network stack of the host or virtual machine. The CPU has to process fewer packets than when LRO is disabled, which reduces its utilization for networking. 5