Lecture 6 -- Storage & File system

Storage devices

a physical component that stores data persistently even when power is off

File system

a structure used to organise & manage files on a storage device, including permissions, size and timestamps

Types of file systems

FAT, ext2, ext3, ext4, XFS

FAT

older, compatible with most operating systems

ext2

older Linux file system without journaling

ext3

improved ext2 with journaling for better recovery

ext4

modern default Linux file system with better performance and larger volume support

XFS

high-performance journaling file system for large data and fast recovery

Inodes

data structures that store metadata about a file such as permissions, ownership and disk location

Partitions

a logical section of a physical storage device that acts as a separate unit

Primary partition

can contain an operating system or file system, limited in number

Extended

a special partition that can contain multiple logical partitions (only one per disk)

Logical partition

partitions created inside an extended partition

swap space

a portion of disk used as virtual memory when RAM is full (slower than RAM)

fdisk

command used to create, delete and manage disk partitions

mkfs

command used to create a file system on a partition (does NOT create partitions)

mount

attaches a file system to a directory so it can be accessed

umount

detaches a mounted file system (cannot unmount if it is in use)

/etc/fstab

a configuration file that defines file systems to be mounted automatically at system boot

LVM (Logical Volume Manager)

a system that manages storages using flexible logical volumes instead of fixed partitions

LVM structure

PV (Physical Volume) - physical storage device

VG (Volume Group)

pool of storage created from Physical Volumes

LV (Logical Volume)

virtual partition created from volume groups

LVM advantages

• allows resizing volumes without rebooting

• combines multiple physical devices into one volume

• simplifies storage management

partition vs file system

• partition = logical section of disk

• file system = structure used to organise data on that partition

mount process

1. create partition (fdisk)

2. create file system (mkfs)

3. mount to directory (mount)

4. persist using fstab

swap vs RAM

• RAM is fast physical memory

• swap is slower disk-based memory used when RAM is full