AIX LVM (Logical Volume Manager)

Physical Volumes (PVs):

A Physical Volume (PV) is any AIX-recognized disk, like hdisk0. It's the base layer of LVM, divided into equal Physical Partitions (PPs), each with a fixed size per VG. Every PV has a unique PVID to prevent mix-ups if device names change after a reboot.

Commands & Examples

# List all PVs

lspv

# Show details of a specific PV

lspv hdisk0

# Assign a PVID to a disk

chdev -l hdisk2 -a pv=yes

# Clear a PVID

chdev -l hdisk2 -a pv=clear

Example lspv output:

hdisk0          00c1a2b3c4d5e678    rootvg      active

hdisk1          00d9e2f3a4b5c678    datavg      active

hdisk2          none                None

(none) indicates the disk has no PVID yet.

Volume Groups (VGs):

A Volume Group (VG) pools one or more PVs into a single logical storage unit. Logical Volumes (LVs) are carved from this pool.

VGDA (Volume Group Descriptor Area): Metadata stored on each PV, containing VG name, PV/LV mapping, and quorum info. Redundant copies ensure recoverability.

Quorum: Ensures that >50% of PVs are active before a VG is used. Prevents corruption. Can be disabled for mirrored or test VGs:

# chvg -Qn rootvg

VG Types Comparison

Feature	Normal VG	Big VG	Scalable VG
Max PVs	32	128	1024–4096
Max PPs/PV	1016	130,048	2,097,152
Max PV Size	~128 GB	1 TB	1 PB
Max VG Size	128 GB	8 TB	4 PB
PP Size Range	1–256 MB	1–256 MB	1 MB–1 GB
Quorum	Yes	Yes	Optional

VG Commands

List all VGs

# lsvg

Show VG details

# lsvg rootvg

Show PVs in VG

# lsvg -p datavg

Show LVs in VG

# lsvg -l datavg

Create VG (Normal/Big/Scalable)

# mkvg -y datavg hdisk1

# mkvg -B -y bigvg hdisk2

# mkvg -S -y scalablevg hdisk3

Add/Remove PV

# extendvg datavg hdisk2

# reducevg datavg hdisk2

Import/Export VG

# importvg -y datavg hdisk1

# exportvg datavg

Physical & Logical Partitions:

Physical Partition (PP): Smallest allocatable unit on a PV. Size fixed per VG (e.g., 4–512 MB).

lsvg datavg | grep "PP SIZE"

Output: 32 megabyte(s)

Logical Partition (LP): Virtual allocation in an LV. 1 LP maps to 1+ PPs.

Example: 100 LPs × 32 MB PP = 3.2 GB LV (6.4 GB mirrored)

Check PV PPs:

# lspv hdisk0

TOTAL PPs: 6399 (204 GB)

Logical Volumes (LVs):

Logical Volumes (LVs) are carved from VGs, acting as virtual disks. They can be used for:

• File systems: JFS2, JFS
• Raw volumes: Databases, paging
• Boot/root volumes
• Mirrored LVs

Commands & Examples

Create LV

# mklv -y lvdata datavg 100   # 100 LPs

List LVs in VG

# lsvg -l datavg

Show LV details and mapping

# lslv lvdata

# lslv -m lvdata

Extend LV

# extendlv lvdata 50  # Add 50 LPs

Remove LV

# rmlv lvdata

Create filesystem on LV

# crfs -v jfs2 -d lvdata -m /data

LV Mapping Example

LP   PP    PV

1    100   hdisk1

2    101   hdisk2

...

Tips & Best Practices

• Always check quorum before performing VG operations.
• Keep VGDA redundancy intact for recovery.
• Start small and scale VGs as storage needs grow.
• Use lsvg -l, lslv -m, and lspv to visualize mappings before critical changes.
• Mirror critical LVs for production systems using mklvcopy.

Assign PVs:

# chdev -l hdisk2 -a pv=yes

# chdev -l hdisk3 -a pv=yes

Create a VG:

# mkvg -S -y appvg hdisk2 hdisk3

Create a mirrored LV:

# mklvcopy -m 2 -y applv appvg 200

Create filesystem and mount:

# crfs -v jfs2 -d applv -m /appdata

# mount /appdata