Download Hard Drive Glossary

Hard Drive Glossary
Access
Access is the action of obtaining data from or writing data into a data storage device.
ANSI
American National Standards Institute.
ATA
Advanced Technology Attachment. ATA was originally defined as a standard for embedded
fixed disk storage on IBM AT compatible PCs and is now the dominant storage interface.
Bit
Bit is an abbreviation for binary digit. A bit can only contain the value 1 or 0. The bit is the basic
data unit for digital computers.
Buffer
The buffer is the storage area used to temporarily store data so that a difference in data
transfer rates and/or data processing rates between sender and receiver can be compensated.
Byte
A byte consists of eight bits.
Cache
Like the buffer, the cache is DRAM (dynamic random access memory) on the hard drive used
to store temporary data that has recently been accessed or data waiting to be written to the
disk.
Capacity
Capacity is the amount of data that can be stored in a given storage device, usually expressed
in bytes.
Channel
A channel (referring to that on a data cable) is a collection of electronic circuits used for data
writing and reading processes to and from magnetic media.
Data
Data is an ordered collection of information.
Gigabyte (GB)
A unit of storage. 1 GB can mean either 1,000,000,000 bytes using the decimal system or
1,073,741,824 bytes using the binary system. Most hard drive manufacturers define 1GB as
1,000,000,000 bytes, while the operating system will treat 1GB as 1,073,741,824 bytes. This is
why the operating system shows the hard drive’s capacity as different to the manufacturer’s
claim.
Jumper
Jumpers are used to set a hard drive’s attributes, such as Master/Slave. A jumper is in
essence a simple on/off switch and when placed over two pins it is the same as closing a
circuit. The combination of one or several jumpers results in different settings.
Latency
Latency refers to the delay that occurs when requesting a specific response. Less latency is
better.
Megabyte (MB)
A unit of storage. 1MB=1,000,000 bytes decimal or 1,048,576 bytes binary. Hard drive
manufacturers usually apply the decimal system while the operation systems apply binary
system of calculating storage capacity.
PATA (Parallel ATA), IDE/EIDE (Enhanced Integrated Drive Electronics)
ATA is the acronym for Advanced Technology Attachment, and it has become an industry
standard hard drive interface for 15 years. ATA uses a 16-bit parallel connection to make the
link between storage devices and motherboards, and is also called PATA to distinguish it from
the newer SATA standard. In additional, ATA is also known as IDE or EIDE (Enhanced
Integrated Drive Electronics). Currently the two most popular standards for ATA hard drives are
the ATA-6 (which is also known as Ultra ATA 100 or Ultra DMA 100) and ATA 133. The
maximum bandwidth for the former is 100MB/s, and 133 MB/s for the latter.
SATA (Serial ATA)
SATA is an interface standard for connecting hard drives to computer systems, and is based
on serial signaling technology. The advantages over PATA include longer, thinner cables for
more efficient airflow within a computer chassis, fewer pin conductors for reduced
electromagnetic interference, and lower signal voltage to minimize noise margin. The
bandwidth of SATA is also far improved over today’s PATA - the SATA 1.0 can reach a
maximum of 1.5Gb/s (150MB/s), while the latest SATA 2.5 standard can support up to 3Gb/s
(300MB/s). As a result of so many advantages, the SATA interface is gradually replacing PATA
as the mainstream hard drive interface in the personal storage market.
SCSI (Small Computer System Interface)
SCSI is a standard interface for transferring data between devices and computers. Thanks to
its outstanding ability to compartmentalize diverse operation, SCSI is very suitable for
multitasking operating environments. Also, SCSI enhances critical performance in situations
where more than one device is connected. Before serial signaling technology was applied into
the SCSI field, all SCSI interface standards used parallel technology to transfer data.
RAID (Redundant Array of Independent/Inexpensive Disks)
RAID is a method of using multiple hard drives together for data storage. A RAID system with
multiple hard drives appears as a single drive to the operating system. Depending on the RAID
level, the benefits provided by RAID is one or more of the following: better throughput,
fault-tolerance or capacity (or something else) when compared to single hard drive.
1. RAID level 0 (or RAID 0) is known as striping, where data is striped across multiple hard
drives. RAID 0 provides the most advanced throughput and capacity, but offers no
fault-tolerance.
2. RAID level 1 (RAID 1) is known as mirroring, which stores the exact same data within at
least two hard drives, this method shows excellent fault-tolerance and reliability, but
delivers less capacity efficiency.
3. RAID level 0+1 and RAID 1+0 are both striping and mirroring, providing good
fault-tolerance and throughput all at the same time.
There are other RAID levels available too, such as RAID level 5 and RAID level 6.
Read
Reading is the action of access a storage location and obtaining the stored data.
Write
Writing is the action of recording data on a storage device.