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Hard Drives
Hard drive or HDD (Hard Disk Drive) is the storage
facility for your computer. It stores every program installed and every change
that is saved. A hard drive doesn’t work as quickly as the other components in
the system that usually do hundreds or even hundreds of thousands of processes
in a second. The HDD sits idle until you open a program or document. It then
pull it out of storage and gives it to the RAM to quickly disperse to the relevant
component.
Most HDDs you see are PATA (Parallel Advanced
Technology Architecture) or commonly referred to as IDE (Integrated Drive
Electronics). Most people are familiar with the size of a HDD, as they are
commonly referred to with the size as the name, “I just got a new 60 GIG hard drive” for
example.
Two type of HDDs commonly seen on the market are
IDE and SATA (Serial Advanced Technology Architecture). IDEs are slower and
cheaper with buss speeds of 100MBs (Mega Bits per Second) or 133MBs and use big
bulky cables that can restrict airflow when left “untucked” (hidden away for a
clean look and cooling purposes). While SATA hard drives are much faster, more
expensive, consume more power, use smaller more efficient wiring and are
capable of 3000+MB/s.
Another difference is in the RPM (Rotations Per
Minute), useful in measuring the amount of time it takes to get information
onto or off the disk. A HDD has spinning platters and works similar to a CD Rom
drive. SATA drives shine here to, pushing upwards of 18,000 RPM whereas IDE hard drives are
limited to 7,200.
HDDs can be installed in different ways to
increase efficiency also. You have probably heard the term RAID (Redundant
Array of Independent Disks) before. This is commonly used technique to control
multiple HDDs for different purposes. Most common RAID configurations:
- RAID-0.
This technique has striping but no redundancy of data. It offers the best
performance but no fault-tolerance.
- RAID-1.
This type is also known as mirroring and consists of at least two drives
that duplicate the storage of data. There is no striping. Read performance
is improved since either disk can be read at the same time. Write
performance is the same as for single disk storage. RAID-1 provides the
best performance and the best fault-tolerance in a multi-user system.
- RAID-2.
This type uses striping across disks with some disks storing ECC (error
checking and correcting) information. It has no advantage over RAID-3.
- RAID-3.
This type uses striping and dedicates one drive to storing information.
The embedded error checking (ECC) information is used to detect errors.
RAID-3 is best for single-user systems with long record applications.
- RAID-4.
This type uses large stripes, which means you can read records from any
single drive. RAID-4 offers no advantage over RAID-5.
- RAID-5.
This type includes a rotating parity array so, all read and write
operations can be overlapped. RAID-5 stores parity information but not
redundant data (but parity information can be used to reconstruct data).
RAID-5 requires at least three and usually five disks for the array. It's
best for multi-user systems in which performance is not critical or which
do few write operations.
HDD load time is something you can live without, but always a joy
to have. Be warned, once you go high speed, its hard to go back!
Where to now? Articles on computer components - How to Choose a PC
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