Hard Disks :

Physically , there are four common types of hard disks ; SSD , SATA , PATA and SCSI. Any logical disk can be Basic or Dynamic .

Basic Disk :

Commonly used in hosting Operating System files. It consists of number of partitions with two styles ; MBR or GPT .

• MBR style can be primary or extended partition , but with limitation of maximum 4 primary partitions. To overcome this issue , there can be a number of logical drives (partitions) under the extended partition.
• GPT style has no limitation of partitions number.

Dynamic Disk :

used in huge storage resources . Hosting OS on it is NOT common and may lead to unexpected errors. It stores data in volumes . There are 5 types of volumes :

• Simple ~ like a normal partition
• Mirrored ~ provides a copy of a volume on another disk
• Striped ~ improves disk input/output (I/O) performance by distributing I/O requests across disks
• Spanned ~ attaching one volume with two physical disks
• RAID-5 ~ like spanned , but more than 2

This type of disks uses databases to track information about volumes and other disks.

Partition table :

records info about primary , extended and logical partitions.

FileSystem :

a method of organizing and storing data on disks in a human readable form. we may see 4 types of filesystem :

• Conventional ~ like ext2 , ext3 ,Btrfs, NTFS
• Flash storage ~ YAFFS
• Databases
• Special purposes ~ sysfs , procfs , debugfs

linux vs. windows FS overview

Everything in Linux is a file or object like a file , even the physical devices.

One can access the existing devices from /dev directory .

Mount :

is a program that instructs the OS that user or application needs to access a certain area(ex. partition) of disk , then OS mount it in a certain space called mount points , where user can access it .

Filesystem Hierarchy Standard in Linux:

In Linux , files and directories are stored in hierarchical form starting from the root represented by ( / ) sign , ending with sub-directories and files.

• etc ~ for configuration
• home ~ all users are allocated in this directory with their home sub-directories
• dev ~ attached devices
• boot ~ bootloader itself and its information
• tmp ~ temporary data
• bin ~ binary files for linux main tools and commands
• lib ~ important libraries

Inode table :

A fact about your photos on social media . Do you know that anyone may track your location , know your device type or even keep sensitive info about you ? That is called MetaData .

Files are stored in table with certain index and some details like :

• Owner of file ~ user or group
• File serial number
• Permissions ~ Read, Write and Execute
• Timestamps of last modifying ,changing or accessing
• Place on disk
• Size
• Number of blocks ( files are stored in something dependent on partition size called blocks )

File types in Linux :

• Normal file ~represented by (-).
• Directory ~ d (like folder in windows)
• Hard link ~ -(another name of existing file)
• Symbolic link ~ l (shortcuts)
• Socket ~ s (passes data between 2 processes)
• Named pipe ~ p (like socket ,but users can’t use it directly)
• Character device ~ c (provides unbuffered direct access to the hardware device)
• Block device ~ b (like character device ,but it always allows the programmer to read or write a block of any size of data — buffered)

Thanks!