Partition of hard drive

In Microprocessing, a partition is part of a Hard drive intended to accommodate a Filesystem.

Partitioning is a fractionation of a real hard drive (material) in several virtual disks (software).

Each partition has its system of Fichier, which will make it possible to store the data then. For recall, the file is the smallest logical entity of storage on a disc. For example, to speak about a partition accommodating a filesystem FAT32, one usually speaks about “partition FAT32”.

A disc can contain one or more partitions. When it contains several partitions, those appear with the operating system like discs (or " volumes") separated. In Windows, they will generally have different letters of reader (C: , D: , etc). In Mac OS, they in general appear each one with its own icon on the Desk. Under Unix, they are hidden under a single tree structure (thus besides that physical peripherals) but are visible through various orders posting the points of assembly (" mount" , " df").

One names partition of starting (sometimes by abuse primary language partition ) that which takes control with starting, that it contains or not the Operating system.

An hard drive can be partitionné for various architectures. There will be thus the partitioning of the type MBR for the majority of the personal computers (PC) or GPT for more recent architectures (Macintosh).

Details with regard to the PC

Tables of partitions

The information on the partitions are stored on the disc itself in zones which one calls tables of partition. The table of principal partition is contained in the first sector of the disc or sector of starting (MBR, Master Boot Record) which also contains the bootstrap routine. Each line of a table of partition contains the address of beginning of the partition and its size. They can be primary partitions which will contain a filing system or wide partitions which will contain in their turn a table of partition having the same structure as the principal table.

Primary partitions

Only the primary partitions can contain the partition of starting of an operating system (Windows, linux…).

However, there exist restrictions on the tables of partitions, some related to the place occupied in the sector of starting of others to simplify the operation of the operating system. In the table of principal partition, one cannot create with more that four partitions, that is to say four primary partitions, from 1 to 3 primary partitions then a wide partition (which often is the last).

Extended partition, logical readers

When one wants more than 4 partitions, thus should be created a wide partition. The latter is neither more nor less than one special primary partition which will contain logical readers.

A wide partition can thus contain several logical readers , who are of unspecified number and are not distinguished for a user's program (nor for the system) from the other partitions.

The logical readers are not directly recognized by BIOS.

The table of wide partition is contained in RBE.

Tools for partitioning

Fdisk : Utility used under DOS, Linux and MacOSX to handle the partitions and the table of starting. Although the name of this tool is identical on these three systems, it is not absolutely about the same program. Under DOS the utility is presented in the form of menus; under Linux, in the form of a tool in line of order (Prompt); under MacOSX, it is necessary to open a Terminal window to use it in an interactive way.
Diskmgmt.msc : Manager of discs delivered with Windows NT /2000/XP to handle the partitions.
DiskDrake : Utility of Mandriva allowing to create, remove, redimensionner partitions in an intuitive and visual way.
Utility of disque.app Administrative of discs delivered with Mac OS X to handle the partitions (named " Volumes" by the Mac system).
Sfdisk : Utility used under Linux to handle the partitions. One of the only utilities being able to be used in noninteractive mode. But attention, apparently risky for the creation of partition.
Cfdisk : Utility used under Linux to handle the partitions. It is presented in the form of menus to the manner of fdisk under DOS.
Pdisk : Utility used under Linux to handle partitions Macintosh on architecture PowerPC.
PartitionMagic : Utility paying of the company Symantec Corporation functioning under DOS or Windows. Norton PartitionMagic is in particular recognized to be able redimensionner, to move or amalgamate one or of the partitions without losing the data which it contains. It allows various operations impossible to realize with the tools provided out of standard by Microsoft as for example to convert a Filesystem NTFS into FAT (the reverse is possible under Windows (NT) thanks to the order convert) or to repair a table of partitions damaged.
Gnu Parted : Utility GNU in line of order or with an graphical interface functioning on the Operating system Linux and allowing to carry out various impossible operations with standard tools like the redimensioning of partitions for example. Parted is actually simply an interface with Libparted, which constitutes really the core of the utility (official page of the Parted project)
QtParted is defined as “a clone of Magic Partition written in C++ by using the graphic library Qt”. This last is in fact an graphical interface with program GNU Parted, or more precisely, libparted. (official site of QTParted)
GParted is an graphical interface with program GNU Parted (libparted). It uses the graphic library GTK and can handle many format of filesystem. (Functionalities of Gparted). To note that Gparted exists in version LiveCD which makes it possible to prepare/modify partitions without system installed on the machine. Official site of Gparted on sourceforge
Testdisk is a program which makes it possible to recover a partition whose table would have been unobtrusive. (official site of testdisk)
Disk director continuation of Acronis, published in France by microapplication under the name Partition continuation 9, is very complete. It allows the formatting, displacement without losses of data, creation, redimensioning, the copy, etc, etc of the partitions of standard sizes and less currents. Moreover one software of management " multi-OS" is provided in order to facilitate the changes of systems without starting again the PC.

Tools for reading of partition

Explore2fs makes it possible to read the contents of a partition ext2 or ext3 since Windows;
Ext2ifs Ext2 Installable File System for Windows
the Mtools give access the contents of partitions FAT since Unix;
MacDrive makes it possible to read and write the contents of hard drives and Cd-ROMs Macintosh (HFS Extended (HFS+) and HFS Standard (HFS)) since Windows.

Identifier of partition

On a computer of the type PC, an identifier associated with each partition makes it possible to know a priori which type of filing system it shelters. This identifier occupies a Octet, with the table of following correspondence:

0 Vacuum 1 FAT12 2 XENIX root 3 XENIX usr 4 FAT16 <32M 5 Wide 6 FAT16 7 NTFS (and its predecessor HPFS) 8 AIX, to see JFS 9 AIX bootable OS/2 Boot Manager has B Win95 FAT32 C Win95 FAT32 (LBA) E Win95 FAT16 (LBA) F Win95 Ext' D (LBA) 10 OPUS 11 Hidden FAT12 12 Compaq diagnosis 14 Hidden FAT16 <32M 16 Hidden FAT16 17 Hidden HPFS/NTFS 18 AST SmartSleep 1b Hidden Win95 FAT32 1c Hidden Win95 FAT32 LBA 1e Hidden Win95 F 24 NEC DOS 39 Plane 9 3c PartitionMagic Recoverable Partition (PqRP) 40 Venix 80286 41 PC Prep Boot 42 SFS 4d QNX 4.x 4th QNX4.x 2nde partition 4f QNX4.x 3rd partition 50 OnTrack DM 51 OnTrack DM6 With 52 CP/M 53 OnTrack DM6 With 54 OnTrackDM6 55 EZ-Drive 56 Bow Goldens delicious 5c Priam Edisk 61 SpeedStor 63 GNU HURD gold Sys 64 Novell Netware 65 Netware Novell 70 DiskSecure Mult 75 PC/IX 80 Old Minix 81 Minix/old Linux 82 Linux Swap 83 This type of partition is used by the filesystems Ext2, Ext3, ReiserFS and JFS 84 OS/2 hidden C: 85 wide Linux 86 NTFS set volume 87 NTFS set volume 8e Linux LVM 93 Amoeba 94 Ameba BBT 9f BSD/OS a0 IBM Thinkpad hi a5 FreeBSD a6 OpenBSD a7 NeXTSTEP a8 Darwin UFS a9 NetBSD ab Darwin boot af HFS+ b7 BSDI fs b8 BSDI swap bb Boot Wizard hid/Acronis Hidden bc Acronis Secure Zone Be Solaris boot c1 DRDOS/sec (FAT c4 DRDOS/sec (FAT c6 DRDOS/sec (FAT c7 Syrinx da Non-FS dated dB CP/M/CTOS/. of Dell Utility df BootIt e1 DOS access e3 DOS reading alone e4 SpeedStor eb BeOS fs ee EFI GPT

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