Performance Optimization Flashcards
7 cards from real COA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Performance Optimization flashcards as text
Which Nova configuration option allows CPU overcommit ratios to be set, enabling more vCPUs than physical cores on a host?
Answer: cpu_allocation_ratio
cpu_allocation_ratio multiplies reported physical CPUs by the given factor, allowing Nova to schedule more vCPUs than physically available.
What Neutron mechanism driver provides the best network I/O performance for bare-metal-like workloads using kernel bypass?
Answer: SR-IOV with ml2 sriovnicswitch
SR-IOV passes virtual functions directly to instances, bypassing the hypervisor network stack for near-native throughput and lowest latency.
In a Ceph-backed Glance deployment, which image format eliminates the conversion overhead during Nova instance boot?
Answer: raw
Raw images are directly usable by Ceph RBD without any conversion, so Nova boots instances from them without a CPU-intensive format conversion step.
Which Heat resource type should be used to implement auto-scaling policies based on Ceilometer/Aodh alarms?
Answer: OS::Heat::AutoScalingGroup
OS::Heat::AutoScalingGroup manages a group of resources that can grow or shrink in response to OS::Heat::ScalingPolicy actions triggered by alarms.
What is the primary performance benefit of enabling NUMA topology awareness in Nova when scheduling instances?
Answer: Instances are placed so their vCPUs and memory reside on the same NUMA node, minimizing cross-node memory latency
NUMA-aware scheduling ensures that instance vCPUs access memory on the same NUMA node, avoiding expensive cross-node memory transfers.
Which oslo.cache backend provides the highest performance for Keystone token caching in a multi-node deployment?
Answer: dogpile.cache.memcached
Memcached provides a shared, high-performance distributed cache accessible by all Keystone nodes, unlike the in-process memory backend which is per-node only.
An operator notices that Nova API response times degrade as the instance count grows. Which database optimization best addresses this?
Answer: Adding indexes on frequently queried columns like project_id, host, and status in the nova_api database
Database query performance degrades with large tables without proper indexes; adding indexes on project_id, host, and status speeds up common Nova API queries.