Partition, Volume, Disk, Drive what is the difference?


Western Digital Raptor X 150 GByte 10,000 rpm.
Western Digital Raptor X 150 GByte 10,000 rpm. A unique hard disk with transparent cover. It was produced in 2006 and was expensive. Really expensive and didn’t appeal to many. It was the trent of transparent PC cases which promote the soecial design of mitherboards, Disks and graffic cards.
 In Windows operating system a user only sees disks when he clicks the computer icon. 

Are they real physical disks? How a disk is configured in Windows?

The story is long and starts from the early home computers. I don’t write personal computers because this is a trademark from IBM, also known as PC. 

_Drive is the machine that reads and writes the storage medium. The medium can be a cassette, a floppy disk, a hard disk, CD, flash memory etc. To be more clear the cassette is medium of data but alone can’t be accessed. It needs a cassette drive. The same with the CD or Floppy Disk. Of course floppy disks drives are obsolete today. However cassette drives still reign in the enterprise computer sector.  

HP digital cassete drive.
HP digital cassete drive. The cassette drives are not dead yet. They offer immense storage at very low price. The only disavantage is that files are not seeked fast.
 The professional cassette drives are very expensive, but the data cassettes still offer immense and the most affordable data storage today. The common HDD and SSD are acronyms for Hard Disk Drive and Solid State Drive. In the case of a HDD the data medium is the hard disk enclosed by a meta box with a motor and heads which read and write data to the disk. In the case of SSD the medium is chips with transistors on an electronic board. Driver and drive are not the same. Drive is hardware, driver is the software which helps the operating system to control the Drive. Usually the operating system includes the proper drivers but some times extra software is needed for an new drive which is named driver. For deep control and informations about the physical drives in windows type DISKPART . DISKPART shows more details and has more commands than the Disk Management. To view the physical drives use the command LIST DISK . The drives are named as DISK 0 for the first, DISK 1 for the second ,DISK 2 for the third etc. What we see at clicking the computer icon of windows is not necessarily physicall drives but partitions or volumes too. For selecting the drive you want to use  type SELECT DISK 0 for the first physical drive or SELECT DISK 1 for the second etc. The command CLEAN erases everything from the selecting disk.

_Partition as the name suggests is a partition of the disk. It is used mainly on HDDs and SSDs. There are many reasons to partition a disk. The first is the economical. Nowadays the rotational hard disks are very cheap and I avoid partitioning. However 15 years ago it was a tool to make a single hard disk very usefull. You can install different Operating Systems on a single hard disk. For example in a single disk I created four partitions. On the first I installed the legendary Windows 98SE, on the second the revolutionary Windows NT 4.0 and on the last two partitions the simple and beautiful Corel Linux. 

Windows NT 4.0 was a game changer.
Windows NT 4.0 was a game changer. Away from the classic DOS provided flexibility and security to disks. It wasn’t very user friendly like windows 98 and lacked harware compability. Actually the very succefull Windows XP is a hybrid of Windows 98 and Windows NT 4.0.
  At the start the first selection of the boot loader was between Linux and Windows and if I selected Windows, the next selection was between Windows 98 or Windows NT 4.0 . For achieving that I had to partition the hard disk into four partitions with different sizes. Linux needs two partitions. Usually the biggest partition was dedicated to Windows 98. 

The  increasing rate of the hard disk capacity is not the same like in Ram or CPUs and it usually surpass the expectations of programmers. My first disk in 1997 was an enormous 6 GByte Quantum and costed 100,000 drachmas around 300 dollars. After 18 years a 6 TByte (6,000 GByte) disk costs the same for one thousand times bigger capacity. In 1997 the windows 95 I had, was recognizing only FAT12 and FAT16 formatting systems. FAT16 however had a limit of two GByte partitions. So I had unwillingly steparated the hard disk into three partitions. After two years in 1999 I installed three operating systems on a single disk and I wanted each operating system to access the files created by the other two operating systems. Windows 98 could recognize only FAT32 and FAT16, Windows NT 4.0 only NTFS and FAT16 and Linux only EXT2 and FAT16. So the common formatting system was FAT16 which restricted the partitions to 2 GByte. Next in 2003 I wanted to have both windows XP and Mandriva Linux which was the successor of my beloved Red Hat linux. Windows XP could recognize FAT32 and NTFS formatting systems and Linux Mandriva EXT2 and FAT32. This time the common formatting system was FAT32. However FAT32 has restrictions. Under Windows XP the biggest partition with FAT32, I could format was 32 GBytes. Also FAT32 doesn’t permit files over 4 GByte. Again I had  created unwillingly many 32 GByte partitions. Nowadays hard disks are very cheap but most laptops don’t have more than one disk. You can’t  install an operating system like windows on a usb hard drive. If you want to have multiple operating systems on a laptop the partitioning is the only way. OS X  and its boot camp is a nice case of multiple operating system on a single disk.

The main kind of partition is the active. The active partition is the partitions which is bootable and usually holds the operating system. Only one partition can be made active. In the case of multiple operating systems on a disk, a boot loader program on the active partition redirects to the selected operating system on different partitions. A hard disk which it isn’t bootable doesn’t need an active partition. Usually the usb hard disks don’t have active partitions.

Under windows FAT32 a disk is restrict to one primary partition and one extended partition. Only the primary partition can be active and only that can have the main files of the operating system. Of course the primary partition can be inactive without operating system.  The extended partition is always subdivided into one or multiple logical partitions. That was a relic of the DOS and windows95,98,Me era. After the windows NT 4.0 and Windows XP and the advent of NTFS formatting system the rules are relaxed and the primary partitions can be as many as four. For a detail view o Partition type DISKPART command and afterwards LIST PARTITION.

The informations about how a disk is partitioned are stored in area which is the old MBR (Master Book Record) or the new GPT (GUID Partition table). In the MBR the informations are stored in one place and if that place is corrupted the data on the disk is unreachable. The GPT store the informations in multiple places and is more robust. The MBR is old and has limitations. Only four primary partitions are permitted and more crucially the biggest drives it can support is 2TByte. That was a big obstacle to the expansion of bigger than 2TByte disks. The GPT is not supported by all 32bit versions of Windows including windows XP,vista,7,8. The 4 GByte limit of memory in a 32bit OS is not such a problem as the 2 TByte hard disk limit. Windows XP 32bit, 64 bit and earlier versions of Windows can’t be installed on GPT disks. The MBR dates back to 1983 and it’s time to be changed.   

A disk under windows can be configured as Basic or Dynamic. A Basic disk support all the properties written before. A dynamic offers RAID capabilities inside Windows without RAID hardware. It is not offered in all versions of windows. It is a premium feature and only professional and above editions provide the RAID functionality of Dynamic discs. The windows don’t use directly the RAID name due to copyright issues. Instead windows uses the spanned, striped and mirrored disk which are equivalent to RAID configurations.

Finally what is Volume? The computer icon on windows shows disks with their assigned letter. That letter distinguishes the Volumes of an operating system. So a volume can be a primary partition, a logical partition, a whole disk, or a combination of dynamic disks (mirror disks, stripped disks or spanned disks). Volume is what the user see and doesn’t have to care what lies behind it. To view the volumes type the command DISKPART and afterwards LIST VOLUMES.


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