Hard disks are for data
storage.
Hard disks are the most
common storage media for everyday use. There
is two main hard disk types used today, IDE and
SCSI hard drives. The IDE drives are cheaper
and is what most PC will be equipped with. SCSI
hard drives are mainly used in servers.
Most computer comes with an
IDE hard disk of 40 Gigabytes and more. This
is the most common type of hard disk and it's
price is lower because of it's wide use
contributing to it's lower production costs.
Most of the time, there is
only one hard disk in a computer, but you can
have more than one. Motherboards usually come
with two embedded IDE ports. Each port can
have two devices connected to it on the same
data cable for a total of four devices. CD and
DVD units are also connected to the IDE ports
and count as one of those four devices.
If your personal computer
has one CD unit and one hard disk, you could
add two devices like two hard disks or one
hard disk and one DVD writer for example. Once
you have four devices, then you can only
replace one device or add a PCI IDE controller
to have more ports to add devices.
Servers will usually be
equipped with SCSI hard drives. SCSI hard
drives are connected to a PCI SCSI controller
that will be able to accept 7 devices for
standard SCSI and 15 for the newer wide SCSI.
There are a lot of different models and
standards and you have to check the
specifications before buying a device to be
sure it's compatible with your controller.
SCSI are mainly used for
servers to be able to have more hard disk
connected to the PC and allow much bigger
storage capability and you can have more than
one controller in a system. The hard disks can
be mirrored or used in a RAID configurations
that allow to recover the data if one of the
hard disk become defective.
There is a new standard
called serial ATA that is a faster and will
eventually replace the IDE standard devices.
Serial ATA is used mainly for external hard
drive devices that connects on a FireWire
port. FireWire ports are not supplied with
most PC computers, so you usually have to buy
and install a PCI FireWire adapter that you
install in a free slot of the computer.
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