Partition table

As a partition table ( English partition table ), also partition scheme ( English partitioning scheme , and partitioning style ) is called standardized data structures that provide information about the division of a data memory contain in separate areas. These areas are known as partitions and are several independently usable parts on a storage medium. Partitions can never overlap, but depending on the specification they can contain (include) other partitions and serve to mark unused areas.

The term partition table includes all forms of partitioning when they use a table; Colloquially, the most widespread partition table contained in the Master Boot Record (MBR) of the IBM-compatible PC is often equated with the term, although this is incorrect. The two partition tables most commonly used and encountered are the already mentioned master boot record and its successor GUID Partition Table (GPT) , German GUID partition table .

Partition tables for hard disk drives were introduced . Due to a lack of capacity, the data carrier was usually not further subdivided into partitions on floppy disks and therefore no partition table was used. On larger data stores such as B. USB sticks , on the other hand, there is almost always a partition table which, however, normally only defines a single partition over the entire storage area.

There are various specifications according to which partition tables can be structured. In the case of the widespread master boot record , the primary partition table including a boot loader is stored within a single data block on a data carrier and comprises precisely 64 bytes, since the MBR partition table consists of 4 entries (4 primary partitions) each 16 bytes (4 × 16 bytes = 64 bytes). According to the specification, the MBR must be stored in the first sector of a data memory, the sector with the number 0, which offers space for 512 bytes with the usual sector size. This leaves 446 bytes for an exchangeable boot loader in x86 - machine code for the IBM PC and compatible computers and 2 bytes for a magic number .

A comprehensive division of data storage at the level of a file system (see Logical Volume Manager ) is not part of the term, but these are mostly based on an existing partitioning using partition tables. Also, RAID configurations that are based on existing partitions partition tables, are possible, as well as the reverse case, that a partition table within an existing RAID configuration is defined.

Designations

As synonymous name has partition scheme , English partition scheme and partition style established. This is also related to the original platform . B. Often the PC partition scheme or the Mac partition scheme is mentioned. However, these names are imprecise because different partition tables are used on these platforms: On the PC with BIOS (up to approx. 2010) it is the master boot record , on the Macintosh up to 2006 it is the Apple Partition Map , while both platforms use EFI or UEFI use the GUID Partition Table (GPT). For a clearer distinction, the MBR partition scheme and GPT partition scheme are also used. But there are also mixed forms, such as GUID partition table scheme or partition table type .

Depending on what is referred to, the MBR partition table is also called MS-DOS partition table or partition scheme ( English DOS type partition table ), because the Master Boot Record was introduced in 1983 with MS-DOS 2.0. But PC partitioning scheme , English PC style partitioning , is a possible name for the partition table in the master boot record .

However, since the terms are very imprecise, context matters. The term partition scheme can also mean the division of partitions for a Unix operating system installation, for example when individual directories are created as separate partitions in accordance with FHS . Under FreeBSD , however, this division is referred to as the partition layout .

Facility

Under most operating systems on PCs partition tables are using a program called fdiskfurnished. There are also a number of other programs for partitioning a hard drive.

Modern operating systems with a graphical user interface usually offer an easy-to-use graphical utility for creating and managing partitions (different partition tables). Under Windows this is the data carrier management , with Linux and BSD distributions a corresponding guided module is usually included in the installation program or a front end based on GNU Parted is usually included. In Mac OS X / OS X / macOS which is in addition to various command line tools Disk Utility included as a graphical partitioning tool.

→ Main article : Partition (disk)

Interoperability

On hard disks for IBM PC compatible computers with BIOS is the Master Boot Record (short: MBR ) as the partition table. Since it is supported on almost all common operating systems and platforms , it has established itself as the de facto standard for partitioning on external storage media (e.g. memory cards , USB sticks , zip disks ). It can therefore be found on devices such as MP3 players or car radios (if a USB stick is plugged in) as well as on all kinds of external storage media.

Because the MBR partition table has a size limit of 2.2 TB , the MBR successor GUID partition table , or GPT for short , has been the new de facto standard since around 2010 on hard drives larger than around 2  TB . This partition table was defined by Intel with the EFI specification around the year 2000 and is intended to remove some of the restrictions of the MBR as its successor. There is therefore a good chance that a device, if it supports storage media with> 2.2 TB storage capacity , can read both MBR and GPT .

Although some kind of partitioning is always possible on storage media, it is by no means necessary. However, some operating systems require a partition table in order to be able to access a storage medium, could consider a storage medium without a partition table to be empty and write to it without asking, or have access restrictions and can only use certain partitions. As the successor to the master boot record , the GUID partition table ( GPT ) also contains an MBR partition table with only one entry, which includes the entire usable space, which marks the disk as occupied for old operating systems and thus protects the contents of the GUID partition table ( see protection MBR ).

On different systems and platforms , specific partition tables are usually required for boot media , often in combination with defined partitions and file systems. Start media are storage media that the startup ( English boot ) can be used. This applies to workstations as well as to u. a. embedded systems and mobile devices . Examples in the area of personal computers are Apple Macintosh with APM up to 2005 and Amiga with Rigid Disk . GUID Partition Table (GPT) is used on modern IBM PC-compatible computers with the BIOS successor UEFI as well as on Apple computers since 2006 .

List of partition tables

• Volume Table Of Contents (before 1980), table of contents on mainframe storage systems
• Master Boot Record (1983), partition table and boot sector on BIOS -based IBM PC-compatible computers
• Apple Partition Map (1987), partition table on m68k and PowerPC based Macintosh computers
• Disklabel (1988), a possible partition table on all BSD operating systems since 4.3BSD Tahoe
• Amiga Rigid Disk , partition table on m68k and PowerPC based Amiga computers
• GUID Partition Table (2000), partition table on EFI -based computers and (from around 2010) on storage media with more than 2 TB storage capacity

See also

• Partition scheme
• Partition (disk)
• Logical Volume Manager
• RAID

Individual evidence

1. ↑ Chapter 2. Installing FreeBSD. 2.6.3. Manual partitioning. In: FreeBSD Handbook. The FreeBSD German Documentation Project, June 10, 2017, accessed June 11, 2017 ( Version 50357 ; Table 2.1. Partitioning Schemes ). 
2. ↑ Windows Setup: Install with the MBR or GPT partition style. In: Windows Deployment Tools Technical Reference. Microsoft , 2017, accessed June 11, 2017 . 
3. ↑ Benjamin Kraft: Reset Mac partition scheme. In: Heise online . May 29, 2015 ( c't 13/2015, p. 152). Retrieved June 11, 2017.
4. ↑ Set up and use an external Mac startup disk. Apple , Inc., accessed June 11, 2017 : "... select the GUID partition table scheme ... before deleting ..." 
5. ↑ Disk Utility for Mac: Use Disk Utility to partition a physical hard drive. Apple , Inc., accessed on June 11, 2017 : " (Note: In the 'System Information:' program), make sure that the type 'GPT (GUID partition table)' is displayed for your storage device under 'Partition table type' ..." 
6. ↑ fdisk - manipulates the hard drive partition table. In: Ubuntu 14.04 LTS manuals. Retrieved June 11, 2017 . 
7. ↑ fdisk (8) - Linux man page. die.net, accessed on June 11, 2017 (English). 
8. ↑ Daniel B. Sedory: An Examination of the MBR (Master Boot Record) code embedded in FDISK.COM for IBM Personal Computer DOS ™ 2:00 . In: The Starman's Realm . July 30, 2003, accessed February 10, 2013 . 
9. ↑ Amit Singh: Mac OS X Internals: A Systems Approach . Addison-Wesley Professional, 2006, ISBN 0-13-270226-6 , pp. 1680 ( full text in Google book search).
10. ↑ 9.15.5. Recommended partition scheme. In: Red Hat Enterprise Linux 6 Installation Guide. Red Hat, Inc., 2017, accessed June 11, 2017 . 
11. ↑ Chapter 2. Installing FreeBSD. 2.6.1. Design a partition layout. In: FreeBSD Handbook. The FreeBSD German Documentation Project, June 10, 2017, accessed June 11, 2017 ( version 50357 ). 
12. ↑ Microsoft TechNet: Disk Management , accessed on 23 December 2013
13. ↑ Apple Support: Disk Utility (El Capitan): Partitioning a Physical Hard Disk , Version dated October 23, 2015; Retrieved September 25, 2016.
14. ↑ FAQ: Drive Partition Limits. (PDF, 246k) UEFI Forum, 2010, accessed on February 18, 2017 (English). 
15. ↑ Frequently asked questions about architecture Disk partitioning GUID table. Further information. In: Help and Support. Microsoft , August 4, 2009, accessed February 10, 2013 : " Removable media without either GUID Partition Table or MBR formatting is considered a" superfloppy. " " 
16. ↑ Andrea Müller: Partition on USB stick inaccessible. In: c't 10/11 hotline. Verlag Heinz Heise , April 26, 2011, accessed on December 23, 2013 (also in issue 10/11, page 164 ).