Disk partitioning

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Disk partitioning or disk slicing is the creation of one or more regions on the hard disk or other secondary storage, so that the operating system can manage the information in each region separately. These areas are called partitions or volumes. This is usually the first step of preparing a newly produced disk, before any file or directory is created. The disk stores information about the location and size of the partition in an area known as the partition table that is read by the operating system before any other part of the disk. Each partition, or volume, then appears on the operating system as a different "logical" disk that uses part of the actual disk. The system administrator uses a program called the partition editor to create, resize, delete, and manipulate partitions. When a hard drive is installed on the computer, it must be partitioned before you can format and use it.

Video Disk partitioning

Manfaat beberapa partisi

Creating more than one partition has the following advantages:

• Separation of operating system (OS) and program files from user files. This allows image backup (or clones) created only from installed operating systems and software.
• Has a separate area for the virtual memory/paging operating system.
• Keep frequently used programs and data close to each other.
• Have separate cache and log files from other files. It can resize dynamically and quickly, potentially making the file system full.
• Use of the multi-boot setting, which allows users to have more than one operating system on a single computer. For example, one can install BSD, Linux, macOS, Microsoft Windows or other operating systems on a different partition from the same HDD and have the option of booting into any compatible operating system when it is turned on.
• Protect or isolate files, to facilitate recovery of damaged file system or installation of operating system. If one partition is damaged, other file systems may not be affected.
• Improve overall computer performance on systems where smaller file systems are more efficient. For example, a large HDD with only one NTFS file system usually has a very large Master File Table (MFT) and usually takes more time to read this MFT than a smaller MFT than a smaller partition.
• Partitions are significantly less than the full size available when unnecessary disk space may reduce the time for diagnostic tools such as checkdisk to run or to backup full images to run.

Maps Disk partitioning

Disadvantages of some partitions

Creating more than one partition has the following flaws, compared to having one partition covering the same disk area:

• Reduce the total available space for user storage on the disk, because it forces the operating system to duplicate a specific file system administration area on disk for each partition.
• Reduce overall disk performance on systems where data is accessed regularly and parallel on multiple partitions, forcing the read/write head of the disk to move back and forth on the disk to access data on each partition and to maintain and update the administrative area files system on each partition. It also prevents disk optimizers from moving all frequently-accessed files closer to each other on the disk, which can reduce the number and range of head movement required. Files can still be moved closer to each other on each partition, but the area itself will still be far apart on disk (see also the concept of "short stroking"). This problem does not apply to Solid-state drives because access times on them are not affected by or dependent on relative sector positions.
• Increases disk fragmentation because it reduces the average size of adjacent free blocks on each partition - compared to one partition with the same overall size - after the same amount of data has been written for them.
• Can prevent the use of all disk capacity, because it can split empty capacity separately. For example, if someone has a disk with two partitions, each with 3 GB free (then totals 6 GB), one can not copy a 4 GB DVD image file on that disk, since no partition will provide enough space for it - although there is more than total total available capacity on disk. If the same files on both partitions are stored on a single partition that covers the entire disk, then the 4 GB file can be easily stored in 6 GB free space.
• Disadvantages portability and may impose limits on how entities can be linked together in the file system. For example, Unix file systems and NTFS file systems allow hard links to be created only as long as links and referenced files are in the same (volume) partition. Also, under Windows if someone is referring a file on another partition, one can do it just by specifying a drive letter assigned partition (or mount point) - which, however, may change with time and depends on the drive being installed. This makes the reference invalid and depends on the actual drive letter assignment, which is not a problem if one should reference files/directories only on the same partition, because in this case one can use relative or relative root-reference directories, without including letters drive/partition.
• Moving files across partitions will require actual copy (bytes), while moving files in partitions generally requires only "meta-data" to be updated.

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PC partition type

This section describes the master boot record partition scheme (MBR), as used historically in DOS, Microsoft Windows and Linux (among other things) on PC-compatible computer systems. In the mid-2010s, most new computers used the GUID Partition Table (GPT) partitioning scheme. For other partitioning scheme example, see general article in partition table.

The total data storage space of the HDD PC where the MBR partition is implemented can contain at most four main partitions , or as an alternative to three main partitions and extended partitions . The Partition Table , located in the master boot record, contains 16-byte entries, each describing the partition.

The partition type is identified by the 1-byte code found in the partition table entry. Some of these codes (like 0x05 and 0x0F ) can be used to indicate an extended partition. Mostly used by the operating system bootloader (which checks the partition table) to decide whether a partition contains a file system that can be used for mount/access to read or write data.

Primary partition

The primary partition contains one file system. In DOS and all early versions of Microsoft Windows systems, Microsoft requires what is called a system partition to be the first partition. All Windows operating systems from Windows 95 and beyond can be placed on (almost) every partition, but the boot files ( io.sys , bootmgr , ntldr , etc.) should be in the primary partition. However, other factors, such as the PC BIOS (see Boot sequence on a standard PC) can also enforce specific requirements for which partition should contain the primary OS.

The partition type code for the primary partition can match the file system contained in (eg 0x07 means NTFS file system or OS/2 file HPFS) or indicates that the partition has a specific usage ( eg 0x82 code usually shows Linux partitions swap ). The FAT16 and FAT32 file systems have used a number of partition type codes due to the limits of different versions of DOS and Windows OS. Although Linux operating systems can recognize a number of different file systems (ext4, ext3, ext2, ReiserFS, etc.), they all consistently use the same partition code type: 0x83 (Linux native file system).

Extended partition

The HDD may only contain one extended partition, but the extended partition can be split into multiple logical partitions. The DOS/Windows system can assign unique drive letters to each logical partition.

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Partitioning schema

DOS, Windows, and OS/2

With DOS, Microsoft Windows, and OS/2, the common practice is to use a single primary partition for the active file system that will contain the operating system, page/swap files, all utilities, applications, and user data. On most Windows consumer computers, C: drive letters are routinely assigned to this primary partition. Other partitions may exist on HDDs that may or may not be seen as drives, such as recovery partitions or partitions with diagnostic or data tools. (Microsoft drive letters do not match partitions in one-to-one mode, so there may be more or fewer drive letters than partitions.)

Microsoft Windows 2000, XP, Vista, and Windows 7 include a 'Disk Management' program that enables the creation, deletion and resizing of FAT and NTFS partitions. Windows Disk Manager in Windows Vista and Windows 7 uses a 1 MB partition alignment scheme that is basically incompatible with Windows 2000, XP, OS/2, DOS, as well as many other operating systems.

Unix-like system

In Unix and Unix-like Unix-like operating systems such as Linux, macOS, BSD, and Solaris, it is possible to use multiple partitions on disk devices. Each partition can be formatted with a file system or as a swap partition.

Some partitions allow directories like/boot,/tmp,/usr,/var, or/home to allocate their own filesystem. Such a scheme has a number of advantages:

• If one of the file systems is corrupted, data outside the file/partition system can remain intact, minimizing data loss.
• Certain file systems can be installed with different parameters, e.g. read-only, or with setuid file execution disabled.
• Running programs that use all the space available on non-system file systems do not populate an important file system.

The general configuration for Linux desktop systems is to use two partitions: one holds the file system installed on the "/" (root directory) and swap partition.

By default, the macos system also uses one partition for the entire file system and uses a swap file inside a file system (like Windows) rather than a swap partition.

In Solaris, partitions are sometimes known as slices . This is a conceptual reference for slicing the cake into sections.

The term "slice" is used in the FreeBSD operating system to refer to the Master Boot Record partition, to avoid confusion with the FreeBSD diskette-based partitioning scheme itself. However, the GUID Partition Table partition is called a "partition" around the world.

Multi-boot and mixed-boot system

A multi-boot system is a computer where users can boot into one of two or more different operating systems (OSs) stored in separate storage devices or in separate partitions of the same storage device. In such systems a menu at startup gives the OS option which to boot/start (and only one OS at a time loaded).

This differs from the virtual operating system, where one operating system is run as a standalone "virtual" program in an already running operating system. (An example is the Windows OS "virtual machine" running from within the Linux OS.)

GUID Partition Table

The GUID Partition Table lobus U nique ID trigger is part of the Unified Extensible Firmware Interface (UEFI) standard for partition table layout on physical hard disk. Many operating systems now support this standard.

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Partition recovery

When the partition is deleted, its entries are removed from the table and the data is no longer accessible. Data remains on the disk until it is overwritten. A special recovery utility, may be able to find lose the file system and recreate the partition table that includes entries for this recovered file system. Some disk utilities may override some of the initial sectors of the partitions they delete. For example, if Windows Disk Management (Windows 2000/XP, etc.) is used to delete partitions, it will overwrite the first sector (sector relative 0) from the partition before deleting it. It is still possible to restore the FAT or NTFS partitions if a backup boot sector is available.

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Compressed disk

HDDs can be compressed to create additional space. In early DOS and Microsoft Windows, programs like Stacker (DR-DOS except 6.0), SuperStor (DRÃ, DOS 6.0), DoubleSpace, or DriveSpace (Windows 95) were used. This compression is done by creating a very large file on the partition, then storing disk data in this file. At startup, device drivers open this file and assign separate mail. Often, to avoid confusion, the original partitions and compressed drives have exchanged letters, so the compressed disk is C:, and uncompressed areas (often containing system files) are named higher.

Source of the article : Wikipedia