Infrastructure as a service Study Guide

📖 Core Concepts Infrastructure as a Service (IaaS) – Cloud model where the provider supplies compute, storage, network, and virtualization that mimics physical hardware. Users manage OS and applications. User control via APIs – High‑level APIs let customers configure backup, scaling, security, and other infrastructure details on demand. Deployment models – Public (shared hardware), Private (dedicated to one org), Hybrid (mix of both, workloads can shift). Utility billing – Charges are based on the amount of resources allocated or actually consumed (pay‑as‑you‑go). 📌 Must Remember IaaS = most basic cloud service (IETF). Control vs. responsibility: Provider → hardware & virtualization; Customer → OS, middleware, apps. Public vs. Private vs. Hybrid: Public = multi‑tenant, lower cost. Private = single‑tenant, higher control/security. Hybrid = combine both, move workloads as needed. Key IaaS components: VM images, block/file/object storage, firewalls, load balancers, IPs, VLANs. Common orchestration platforms: OpenStack, Apache CloudStack, OpenNebula. Hypervisor families: Xen, KVM, VMware ESX/ESXi, Microsoft Hyper‑V, Oracle VM/VirtualBox. Containers run directly on the host kernel → higher performance (no hypervisor overhead). 🔄 Key Processes Provision a VM User requests VM via API → Orchestration platform selects a hypervisor host → Hypervisor boots the VM as a guest. Scale resources on demand API call → Orchestrator allocates additional CPU/Memory/Storage → Updated usage tracked for billing. Migrate a VM (live migration) Hypervisor copies memory state → Switches VM execution to new host → No downtime, useful for load balancing or maintenance. 🔍 Key Comparisons IaaS vs. PaaS – IaaS: you manage OS & apps; PaaS: provider also manages OS/runtime. Public Cloud vs. Private Cloud – Public: shared resources, lower cost; Private: dedicated resources, greater isolation. Hypervisor vs. Container – Hypervisor: full VM abstraction → more isolation, higher overhead. Container: kernel‑level isolation → less overhead, shares OS kernel. ⚠️ Common Misunderstandings “IaaS means no maintenance.” – Only hardware & virtualization are managed by the vendor; you still patch the OS and apps. “Containers are a type of VM.” – Containers are not VMs; they run directly on the host kernel, not on a hypervisor. “Hybrid cloud = two separate clouds.” – Hybrid implies orchestrated integration, allowing seamless workload migration. 🧠 Mental Models / Intuition “Lego bricks” analogy – IaaS provides the bricks (CPU, RAM, storage, network). You build whatever you need on top, while the vendor supplies the base plate and keeps it sturdy. “Control knob” model – Think of the API as a dial: turn it up to add resources, turn it down to release them, and the meter (billing) follows. 🚩 Exceptions & Edge Cases Dedicated carrier clouds (VPN, private lines) may be required for compliance; not all public‑Internet connections are allowed. Some providers expose bare‑metal servers (no virtualization) as an IaaS offering – breaks the typical “virtualization” expectation. 📍 When to Use Which Choose Public IaaS when you need rapid scaling, low upfront cost, and can tolerate multi‑tenant security. Choose Private IaaS for strict regulatory/compliance needs, predictable workloads, or when you require dedicated hardware. Hybrid is ideal when you want to run sensitive data on‑prem (private) but burst to the public cloud for peak loads. Use Containers for micro‑services or high‑performance workloads where you want minimal overhead. Use full VMs when you need strong isolation, different OS kernels, or legacy applications. 👀 Patterns to Recognize API‑first phrasing in questions → likely about scaling, backup, or security configuration. “Pay‑as‑you‑go” cost wording → points to IaaS utility billing vs. fixed‑price contracts. Mention of “hypervisor” → expect VM lifecycle or migration concepts. Reference to “VLAN”, “IP address”, “load balancer” → signals IaaS service‑component knowledge. 🗂️ Exam Traps Distractor: “IaaS includes OS management.” – Wrong; OS is the customer’s responsibility. Distractor: “Containers provide hardware‑level isolation.” – Containers share the kernel; isolation is at the OS‑level. Distractor: “Hybrid cloud = two independent clouds.” – Hybrid requires orchestration for workload movement. Distractor: “Billing is always based on allocated resources.” – Some models bill on actual consumption; watch for phrasing. Distractor: “All IaaS providers use the same hypervisor.” – Providers may offer multiple hypervisors; the choice can affect features like live migration.