Acronis disk director suite 9.0 User Manual
Hard Disk And Operating System
106
Copyright © Acronis, Inc., 2000–2005
Appendix A. Hard Disk And Operating
System
System
Appendices contain additional information about hard disk construction and data
storage, partitions, file systems and interaction of operating systems with hard
disks.
storage, partitions, file systems and interaction of operating systems with hard
disks.
A.1
Hard Disk Organization
All hard drives have basically the same structure. Inside the case, there are
several disks with a magnetic coating set on a single axis (spindle). A special
motor provides the necessary rotation speed to the spindle, e.g. 5,400 rpm,
7,200 rpm, or 10,000 rpm.
several disks with a magnetic coating set on a single axis (spindle). A special
motor provides the necessary rotation speed to the spindle, e.g. 5,400 rpm,
7,200 rpm, or 10,000 rpm.
Information on disks resides on concentric tracks. Each track has a number.
The outermost track is number 0, and the numbers grow inwards.
The outermost track is number 0, and the numbers grow inwards.
Each of the tracks is divided into sectors that contain minimal information blocks
that can be written to the disk or read from it. Sectors also have numbers. On
every disk, there is a marker that indicates the beginning of sector enumeration.
The sector that is the closest to this marker is number 1.
that can be written to the disk or read from it. Sectors also have numbers. On
every disk, there is a marker that indicates the beginning of sector enumeration.
The sector that is the closest to this marker is number 1.
At the beginning of a sector, there is a header (prefix portion) that marks the
beginning of the sector and its number. At the end of a sector in the suffix
portion, a checksum is used to check data integrity. The data area between the
prefix and suffix portions is 512 bytes in size.
beginning of the sector and its number. At the end of a sector in the suffix
portion, a checksum is used to check data integrity. The data area between the
prefix and suffix portions is 512 bytes in size.
Both sides of each disk on the spindle are used to store data. All tracks that have
the same number on all the surfaces of all disks comprise a cylinder. For each
work surface of a disk in the drive, there is a head that enables reading and
writing data from/to the disk. Heads are assembled into a block and are
numbered, starting with 0.
the same number on all the surfaces of all disks comprise a cylinder. For each
work surface of a disk in the drive, there is a head that enables reading and
writing data from/to the disk. Heads are assembled into a block and are
numbered, starting with 0.
To perform an elementary read or write operation, the head block should be
positioned at the necessary cylinder. When the appropriate sector (with the
appropriate number in the service area) of the rotating disks approaches the
head, data is exchanged between the head and the electronic circuit board of the
disk drive.
positioned at the necessary cylinder. When the appropriate sector (with the
appropriate number in the service area) of the rotating disks approaches the
head, data is exchanged between the head and the electronic circuit board of the
disk drive.
Sector structure of a hard disk is created via low-level formatting during which
each of the tracks of the disk is marked up. This process generally takes place
when the drive is manufactured.
each of the tracks of the disk is marked up. This process generally takes place
when the drive is manufactured.
Modern disk drives usually contain relatively few magnetic disks (1–2) to make
the head block lighter and speed up access to sectors (a drive like this has 2–4
heads respectively).
the head block lighter and speed up access to sectors (a drive like this has 2–4
heads respectively).