Architecture & System Design 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 Architecture & System Design flashcards as text
Which approach best describes how Swift achieves durability without traditional RAID?
Answer: Storing multiple replicas (or erasure-coded fragments) across distinct failure domains (zones/regions)
Swift achieves durability through replica placement across distinct failure zones (nodes, racks, data centers), so no single hardware failure can cause data loss.
In OpenStack Keystone, what is the difference between a 'domain' and a 'project'?
Answer: A domain is a top-level namespace for users and projects; a project is a resource allocation boundary within a domain
A Keystone domain is an administrative namespace containing users, groups, and projects, while a project (formerly tenant) is the resource quota and ownership boundary.
What is the purpose of host aggregates in Nova, and how do they differ from availability zones?
Answer: Host aggregates are admin-defined groupings of hosts with metadata used for scheduling; availability zones are a user-visible subset of host aggregates
Host aggregates allow admins to tag compute hosts with metadata for scheduler filtering; an availability zone is simply a host aggregate whose metadata is exposed as a user-selectable zone.
During a rolling upgrade of OpenStack services, which service must typically be upgraded first to maintain compatibility across mixed-version deployments?
Answer: Keystone
Keystone is upgraded first because all other services depend on it for authentication; a compatible Keystone must be in place before API services begin accepting tokens from a new version.
What is the recommended method for passing user data (e.g., cloud-init scripts) to a Nova instance at boot time?
Answer: Providing a user_data parameter in the instance creation request, accessed via the metadata API at 169.254.169.254
User data is passed via the nova boot --user-data parameter and is retrievable inside the instance from the EC2-compatible metadata service at 169.254.169.254.
When configuring Neutron with the ML2 plugin, what is the role of a 'mechanism driver'?
Answer: It implements the actual network plumbing on the underlying infrastructure (e.g., OVS, OVN, LinuxBridge)
ML2 mechanism drivers implement how virtual network constructs are realized on the physical or virtual infrastructure, such as configuring OVS flows or OVN logical switches.
Which OpenStack component would you configure to automatically remediate a failed Nova instance by restarting it on another compute host?
Answer: Masakari (Instance HA service)
Masakari provides automated instance recovery by detecting host or instance failures and evacuating or restarting affected instances on healthy compute nodes.