Linux - Linux Storage Architecture

Linux storage is built in layers, and each layer has a specific purpose.
From physical disks → partitions → LVM → RAID → filesystem → mount points → applications.

Let’s break it down simply.

1. Physical Storage Layer

This is the hardware layer.

Examples:

  • HDD (/dev/sda)

  • SSD (/dev/nvme0n1)

  • USB drives (/dev/sdb)

  • SAN/NAS devices (iSCSI, Fibre Channel)

Linux detects storage as block devices, accessible under:

/dev/

Examples:

  • /dev/sda

  • /dev/sdb

  • /dev/nvme0n1

You can list them with:

lsblk

2. Partition Layer

Each disk can be divided into partitions, using:

  • MBR (older)

  • GPT (modern)

Tools:
fdisk, gdisk, parted

Example partitions:

  • /dev/sda1

  • /dev/sda2

Partitioning is used to separate:

  • OS

  • Home directory

  • Swap

  • Data storage

3. RAID Layer (Optional)

RAID combines multiple physical disks to improve performance, redundancy, or capacity.

Example RAID array device:

  • /dev/md0

Tools:

  • Hardware RAID (RAID controller)

  • Software RAID (mdadm)

RAID sits on top of physical disks, but below LVM/filesystem.

4. LVM Layer (Logical Volume Manager) (Optional but common)

LVM gives flexible storage management:

  • Resize filesystem easily

  • Combine disks

  • Create snapshots

  • Add/remove storage dynamically

Components:

  • PV (Physical Volume) → created from partitions/disks

  • VG (Volume Group) → storage pool

  • LV (Logical Volume) → partitions inside VG

Example:

  • Physical: /dev/sda1

  • PV: created with pvcreate /dev/sda1

  • VG: /dev/vgdata

  • LV: /dev/vgdata/lvhome

LVM sits above RAID and below filesystem.

5. Filesystem Layer

Once you have a partition or logical volume, you format it with a filesystem.

Common Linux filesystems:

  • ext4 (most common)

  • xfs (enterprise, performance)

  • btrfs (snapshots + compression)

  • vfat/ntfs (USB/Windows)

Command example:

mkfs.ext4 /dev/vgdata/lvhome

The filesystem manages:

  • File storage

  • Directory structure

  • Journaling

  • Metadata

6. Mount Layer

Mounting makes the filesystem accessible from the Linux directory tree.

Linux uses a single unified directory tree starting at /.

Mount command:

mount /dev/vgdata/lvhome /home

Mount points can be:

  • /home

  • /var

  • /srv

  • /mnt/data

  • /media/usb

Persistent mounts go into:

/etc/fstab

7. Application Layer

Finally, applications and users access files using:

  • Commands (cp, mv, ls)

  • Services (databases, webservers)

  • APIs

They don’t care about:

  • RAID

  • LVM

  • Hardware

  • Filesystem
    … these are abstracted by the OS.

Linux Storage Architecture – Layer Diagram

┌───────────────────────────────┐
│          Applications         │
└───────────────▲───────────────┘
                │
┌───────────────┴───────────────┐
│       Mount Points (/mnt)      │
└───────────────▲───────────────┘
                │
┌───────────────┴───────────────┐
│        Filesystems (ext4)      │
└───────────────▲───────────────┘
                │
┌───────────────┴───────────────┐
│          LVM (PV/VG/LV)        │
└───────────────▲───────────────┘
                │
┌───────────────┴───────────────┐
│      RAID Arrays (/dev/md0)    │
└───────────────▲───────────────┘
                │
┌───────────────┴───────────────┐
│ Partitions (/dev/sda1/sda2)    │
└───────────────▲───────────────┘
                │
┌───────────────┴───────────────┐
│   Physical Disks (/dev/sda)    │
└───────────────────────────────┘

Putting It All Together — Example Path

A typical server might look like:

Physical Disk → Partition → RAID 5 → LVM → ext4 → Mounted on /data → App uses it

Example device:

/dev/md0 → /dev/vgdata/lvdata → /data

Advantages of This Layered Architecture

✔ Flexibility (LVM)
✔ Reliability (RAID)
✔ Easy expansion of storage
✔ Modular (change one layer without touching others)
✔ Good performance + safety

In Summary

Linux storage is built in layers:

  1. Physical disks

  2. Partitions

  3. RAID (optional)

  4. LVM (optional)

  5. Filesystem (ext4/xfs)

  6. Mount points

  7. Applications

This layered architecture gives Linux powerful, flexible, and reliable storage management.