3.2.2. Volume Types and Logical Volume Management

💡 First Principle: Raw partitions are fixed in size—once created, resizing them requires downtime. Logical Volume Management (LVM) adds a layer of abstraction that allows volumes to be resized, moved, and managed dynamically without repartitioning physical drives.

Windows Volume Types

• Basic disk: The default. Contains primary partitions, extended partitions, and logical drives. Simple and well-understood but inflexible—resizing requires third-party tools or partition manipulation.
• Dynamic disk: Enables software RAID (spanned, striped, mirrored, RAID-5 volumes) and volume extension across multiple physical disks within Windows. Dynamic volumes cannot be accessed by other OS installations or during recovery without specialized tools.

LVM (Logical Volume Management) — Linux

LVM adds three layers between physical disks and the file system:

Physical Volumes (PVs) — actual disks or partitions
        ↓
Volume Groups (VGs) — pool of storage from one or more PVs
        ↓
Logical Volumes (LVs) — virtual partitions carved from the VG

This abstraction enables:

• Online resizing: Extend or shrink volumes without unmounting (with compatible file systems)
• Snapshots: Point-in-time copies of a volume for backup or testing
• Thin provisioning: Allocate more logical space than physical space exists (storage grows on demand)
• Spanning: Spread a single volume across multiple physical drives

Page/Swap/Scratch Space

Every OS uses virtual memory when RAM is exhausted:

• Windows: Page file (pagefile.sys)—used to extend virtual memory and for crash dump creation
• Linux: Swap partition or swap file—used when RAM is full; should be sized based on RAM and use case
• VMware: two different things share the "scratch/swap" vocabulary — the scratch partition is not virtual memory. It stores logs, core dumps, and diagnostic output. ESXi's actual virtual memory is the separate VMkernel swap (and per-VM .vswp files). A question about ESXi running out of scratch is a logging/diagnostics problem; a question about ESXi swapping is a memory-overcommit problem

Location and size matter: place swap on fast storage (SSD if possible) and away from heavily loaded partitions. A full swap partition causes system instability.

⚠️ Exam Trap: Dynamic disks in Windows are not the same as Windows Storage Spaces (a newer technology). The exam covers dynamic disks as a legacy feature; understand the difference if asked about software RAID within Windows.

Reflection Question: A Linux server's file system has no more room to grow, but the disk has unallocated space. What Linux storage feature allows you to extend the mounted file system without downtime?