Managing disks is the primary job of Linux administrators. Linux disk management includes many technical terms. Understanding these terms is the first step in building an effective Linux disk management strategy.
Types of hard disks
There are two types of hard disks: HDD and SSD. HDDs use magnet-coated platters to store data. SSDs use integrated circuits to store data. HDDs are cheaper than SSDs but provide slower data transfer speeds.
SSDs are costly but more durable and provide faster data transfer speeds than the traditional HDDs. Generally, administrators use both types of hard disks. They use HDDs to store data and SSDs to install operating systems and applications.
Serial and parallel transmission
An interface connects a hard disk to the motherboard. An interface can use one of two types of transmissions: serial and parallel. In serial, it sends one bit at a time. In parallel, it sends multiple bits at the same time.
Hard disk Interfaces
We have four interfaces to connect a hard disk to the motherboard. These interfaces are SCSI, PATA, SATA, and NVMe.
SCSI was developed as a common interface to connect multiple devices to the motherboard. It uses a SCSI cable to connect devices to the motherboard. Originally, it was developed for parallel transmission. Later, it was upgraded for the serial transmission as well. You can use it to connect printers, scanners, and hard disks to the motherboard. It can transfer data up to 80 Mbps. This interface is no longer used in personal computers.
PATA was developed in 1986. It uses parallel transmission. It is also known as IDE. It uses an IDE cable to connect hard disks to the motherboard. It can transfer data up to 133 Mbps. This interface is also outdated.
SATA was developed in 2003. It uses serial transmission. It uses a serial cable to connect the hard disk to the motherboard. It is available in generations. The first generation SATA was launched as a 1.5 Gbps interface. The latest generation SATA is the third generation. It can transfer data up to 6 Gbps.
NVMe is a new interface type. Unlike SCSI, PATA, and SATA, it does not use a cable to connect the hard disk to the motherboard. It is available as a slot on the motherboard. It supports only SSD disks. It can transfer data up to 32 Gbps.
BIOS/UEFI
BIOS (Basic Input Output System) and UEFI (Unified Extensible Firmware Interface) are two frameworks motherboards use to boot systems. BIOS is a classic framework, while UEFI is a modern framework.
BIOS works in 16-bit mode. The 16-bit mode limits the amount of code that can be read and executed. Due to this limitation, BIOS recognizes and supports storage devices up to 2 TB. If you have a hard disk bigger than 2 TB, the BIOS-based system will not recognize it.
UEFI (Unified Extensible Firmware Interface) is low-level software. It was developed to address the limitations of BIOS. It works similarly to BIOS but supports storage devices of all sizes and many modern features that make framework management easier and more secure.
It works in 32-bit and 64-bit modes. It can boot from a disk larger than 2 TB. It provides a graphical user interface, which is easier to use than the old terminal interface in BIOS.
Partitions
We cannot use a blank hard disk to store data. We can save data on it only when it has a file system. We can create a file system only on a partition. Therefore, if we want to use a hard disk, first, we need to create partitions on it. We can create a single partition or multiple partitions as per our requirements.
Partitions provide the following benefits.
They allow us to distinguish between different types of data. For example, we can save media contents on one partition and text contents on another partition.
They allow us to customize the security policy. For example, we can define a high-security policy on the partition having the sensitive data and a normal security policy on the partition having the regular data.
They allow us to create a backup strategy where only relevant portions of the OS are backed up.
They improve system performance and stability. For example, if one partition fills up completely, you can transfer its data to another partition having space.
File systems
A file system is a logical container used to store files and directories. We can create a separate file system on each partition or can use the same file system on all partitions. Linux supports several file system types such as EXT, EXT2, EXT3, EXT4, XFS, VFAT, NTFS, SWAP Space, LVM, and RAID
MBR / GPT
A hard disk saves partition information in a partition table. There are two methods to store the partition table on the hard disk: MBR and GPT.
MBR is a classical method to store the partition table. It uses the first 512 bytes of the hard disk to save the partition and boot loader information. Of these 512 bytes, it uses only 64 bytes to store the partition table. Since it uses only 64 bytes to store the partition table, the partition table can store information about only 14 partitions.
GPT is a modern method to store the partition table. It uses 4Kb space to store partition information and boot loader program. Its partition table can store information about 128 partitions.
