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Capacity
Capacity is the maximum amount of data a drive or disk(for example, a DVD disk) can store. Typical hard disk storage capacities today are either in gigabytes or terabytes. These sizes store enormous amounts of data. This is very useful when saving music and video, especially video files, which are extremely huge.
RPM
RPM (Revolutions Per Minute)- Within a hard disk case are round platters (the actual disks) that are attached to a spindle that spins. The disks are written to or read from while spinning. One revolution is how many times the platters make a complete rotation. Disks in a HDD literally rotate thousands of times per minute. The greater the RPM, the faster data is read or written. 7200 RPM is mainly what you see on home computers.
Form Factor
The form factor of a hard drive is the actual physical size of the case the platters are in. The main sizes are 3.5in and 2.5in.
Cache Memory
A small amount of memory, usually 8, 16, or 32MB, is set aside for the most frequently accessed files. When one of these files is selected, it is retrieved from the cache. This reduces access time since the system does not have to search the drive for the data.
Capacity is the maximum amount of data a drive or disk(for example, a DVD disk) can store. Typical hard disk storage capacities today are either in gigabytes or terabytes. These sizes store enormous amounts of data. This is very useful when saving music and video, especially video files, which are extremely huge.
RPM
RPM (Revolutions Per Minute)- Within a hard disk case are round platters (the actual disks) that are attached to a spindle that spins. The disks are written to or read from while spinning. One revolution is how many times the platters make a complete rotation. Disks in a HDD literally rotate thousands of times per minute. The greater the RPM, the faster data is read or written. 7200 RPM is mainly what you see on home computers.
Form Factor
The form factor of a hard drive is the actual physical size of the case the platters are in. The main sizes are 3.5in and 2.5in.
Cache Memory
A small amount of memory, usually 8, 16, or 32MB, is set aside for the most frequently accessed files. When one of these files is selected, it is retrieved from the cache. This reduces access time since the system does not have to search the drive for the data.
Types of Drives
Now that the basics have been covered, let's look at some different kinds of drives.
Two main types are used by home PCs and laptops: IDE/EIDE and Serial ATA. Serial ATA is discussed on the following page.
IDE (Integrated Drive Electronics)
The IDE interface standard has been around for a very long time. The term interface in this sense means how the drive connects to the motherboard. As improvements were developed it later was called EIDE for Enhanced IDE. And after even further developments it has also come to be known as ATA (Advanced Technology Attachment). These drives connect to the motherboard via a flat, 80-wire cable to an IDE connector. Two drives can be attached on one cable.
Now that the basics have been covered, let's look at some different kinds of drives.
Two main types are used by home PCs and laptops: IDE/EIDE and Serial ATA. Serial ATA is discussed on the following page.
IDE (Integrated Drive Electronics)
The IDE interface standard has been around for a very long time. The term interface in this sense means how the drive connects to the motherboard. As improvements were developed it later was called EIDE for Enhanced IDE. And after even further developments it has also come to be known as ATA (Advanced Technology Attachment). These drives connect to the motherboard via a flat, 80-wire cable to an IDE connector. Two drives can be attached on one cable.
Every computer must have a hard disk drive (commonly called a hard drive, hard disk, or abbreviated HDD). Your operating system is stored on the hard drive. Of course any other file can be saved there too. It is the main location where people save data. Having adequate hard disk storage for your needs is important. The main purpose of this page explains the difference between a IDE and SATA hard drive, although a brief description of SCSI, solid state, and flash drives are discussed as well. But first I explain some common terminology.
Speed and Bus Interface
The speed of a hard drive is determined by how fast the connector can send data. Currently the primary drive rates are 100 MB/s
and 133 MB/s - 133 MB/s being the maximum. These hard disks are commonly described by the abbreviation "ATA" followed by the
speed of its connector (ATA 100, ATA 133).
IDE drive connectors use a parallel bus, meaning multiple bits are transmitted simultaneously. To distinguish between Serial ATA drives, IDE disks are also referred to as PATA (the "P" stands for parallel).
The speed of a hard drive is determined by how fast the connector can send data. Currently the primary drive rates are 100 MB/s
and 133 MB/s - 133 MB/s being the maximum. These hard disks are commonly described by the abbreviation "ATA" followed by the
speed of its connector (ATA 100, ATA 133).
IDE drive connectors use a parallel bus, meaning multiple bits are transmitted simultaneously. To distinguish between Serial ATA drives, IDE disks are also referred to as PATA (the "P" stands for parallel).
To make it a little less confusing, here are some different names for IDE:
EIDE (Enhanced IDE)
ATA (Advanced Technology Attachment)
PATA (Parallel ATA)
Although there are still IDE drives around, Serial ATA is now the dominant standard, discussed next.
EIDE (Enhanced IDE)
ATA (Advanced Technology Attachment)
PATA (Parallel ATA)
Although there are still IDE drives around, Serial ATA is now the dominant standard, discussed next.
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Serial ATA (SATA)
Today, SATA disk drives are the dominant standard and use a serial interface to transfer data, i.e., data is transmitted one bit at a time. Using a faster clock rate, sending one bit is faster than sending several with a slower clock, as with IDE. Data also travels along a single wire, reducing inteference. With SATA, one path is used for sending and another for receiving. With PATA, data is sent and received on one path.
The original SATA standard has a transfer rate of 150 MB/s (SATA-150). Now SATA can transmit up to 300 MB/s (SATA II or SATA-300), and 6 Gb/s (SATA 3), far surpassing PATA's 133 MB/s. SATA uses a 7-wire cable for connecting to the motherboard.
Today, SATA disk drives are the dominant standard and use a serial interface to transfer data, i.e., data is transmitted one bit at a time. Using a faster clock rate, sending one bit is faster than sending several with a slower clock, as with IDE. Data also travels along a single wire, reducing inteference. With SATA, one path is used for sending and another for receiving. With PATA, data is sent and received on one path.
The original SATA standard has a transfer rate of 150 MB/s (SATA-150). Now SATA can transmit up to 300 MB/s (SATA II or SATA-300), and 6 Gb/s (SATA 3), far surpassing PATA's 133 MB/s. SATA uses a 7-wire cable for connecting to the motherboard.
SATA Motherboard Connectors
7-Pin Connector (Center), Power Connector (Right)
One of the primary uses for SATA drives is RAID. RAID is an acronym that stands for Redundant Array of Independent Disks.
It copies data from one drive to another and can involve more than two disks. In order to set up RAID, a motherboard has to suppport it.
There are several ways to implement RAID, and each type is numbered (RAID 0, RAID 1, RAID 2, etc). On a PC, it's usually 0, 1, or a conbination of the two that's commonly used, so those will be the focus on this site.
RAID 0 (Striping)
In a striping system, hard drives are seen by the computer as a single drive. For example, if a PC contains two 80 GB drives, it sees it as one 160 GB disk.
with striping, files are split and copied to each drive simultaneously. The whole idea behind this technique is that by splitting files, it will take less time writing each piece to both disks(assuming you are just using only two drives, you can use more) than it will take writing the entire file to a single disk, as is the case in a non-RAID machine. This also increases the access time of a file.
RAID 1 (Mirroring)
With mirroring, you're really just backing up a drive. All the contents of a drive are copied to another without any file splitting, so in this case, the second disk is an exact replica of the first. If the primary drive goes bad, you have another duplicate copy.
Combinations
RAID 0+1: Requires at least four drives. The first two use striping and the second pair provides the backup (mirroring). If a disk fails, then the system performs striping.
RAID 1+0: (Also written as RAID10): It's like RAID 0+1 except upon a disk failure, the system performs mirroring.
It copies data from one drive to another and can involve more than two disks. In order to set up RAID, a motherboard has to suppport it.
There are several ways to implement RAID, and each type is numbered (RAID 0, RAID 1, RAID 2, etc). On a PC, it's usually 0, 1, or a conbination of the two that's commonly used, so those will be the focus on this site.
RAID 0 (Striping)
In a striping system, hard drives are seen by the computer as a single drive. For example, if a PC contains two 80 GB drives, it sees it as one 160 GB disk.
with striping, files are split and copied to each drive simultaneously. The whole idea behind this technique is that by splitting files, it will take less time writing each piece to both disks(assuming you are just using only two drives, you can use more) than it will take writing the entire file to a single disk, as is the case in a non-RAID machine. This also increases the access time of a file.
RAID 1 (Mirroring)
With mirroring, you're really just backing up a drive. All the contents of a drive are copied to another without any file splitting, so in this case, the second disk is an exact replica of the first. If the primary drive goes bad, you have another duplicate copy.
Combinations
RAID 0+1: Requires at least four drives. The first two use striping and the second pair provides the backup (mirroring). If a disk fails, then the system performs striping.
RAID 1+0: (Also written as RAID10): It's like RAID 0+1 except upon a disk failure, the system performs mirroring.
SCSI Drives
SCSI (Pronounced "scuzzy") stands for Small Computer Systems Interface, and was originally developed to replace IDE before Serial ATA came about. In addition to hard drives, other devices can be SCSI. Because PCs use either IDE or Serial ATA drives, I am not going to go into a lot of detail about SCSI. But I do want you to know that it exists and a PC is capable of using a SCSI drive.
SCSI is much more faster than IDE. Several types developed over time: Narrow, Wide, Fast, Fast Wide, and Ultra. These refer to how much and how fast data is sent for each standard. The only one in use today is Ultra, itself consisting of various types. 8 or 16 devices are supported on one cable, depending on which kind is implemented. SCSI devices are a little more troublesome to configure than IDE and SATA and generally tend to be more expensive.
SCSI (Pronounced "scuzzy") stands for Small Computer Systems Interface, and was originally developed to replace IDE before Serial ATA came about. In addition to hard drives, other devices can be SCSI. Because PCs use either IDE or Serial ATA drives, I am not going to go into a lot of detail about SCSI. But I do want you to know that it exists and a PC is capable of using a SCSI drive.
SCSI is much more faster than IDE. Several types developed over time: Narrow, Wide, Fast, Fast Wide, and Ultra. These refer to how much and how fast data is sent for each standard. The only one in use today is Ultra, itself consisting of various types. 8 or 16 devices are supported on one cable, depending on which kind is implemented. SCSI devices are a little more troublesome to configure than IDE and SATA and generally tend to be more expensive.
External Drives
Hard disk drives can connect externally to a computer. The drive is placed in a case called an enclosure that contains a port(s) on the back for connecting to the computer via a cable. For quite some time enclosures used USB or Firewire. Now, many support any combination of USB, Firewire, and External SATA (eSATA) ports on the same encasement. External SATA is far faster than USB and Firewire. To use it, a computer must also have an eSATA connector. If it doesn't, a card can be purchased with the interface on it.
Hard disk drives can connect externally to a computer. The drive is placed in a case called an enclosure that contains a port(s) on the back for connecting to the computer via a cable. For quite some time enclosures used USB or Firewire. Now, many support any combination of USB, Firewire, and External SATA (eSATA) ports on the same encasement. External SATA is far faster than USB and Firewire. To use it, a computer must also have an eSATA connector. If it doesn't, a card can be purchased with the interface on it.
Enclosures are manufactured to match the form factor of particular drive.
Solid State Drives
Solid State Drives, or SSDs, differ from traditional hard drives in that they contain flash memory rather than a motor, spinning platters, and a read/write head. A big advantage is that you do not have to concern yourself with drive failure due to some mechanical problem, and they require much less power to run.
Like standard drives they come as internal or external, IDE or SATA. Most are 2.5 inches.
A big disadvantage with solid state hard drives, however, is capacity and cost. Presently, most come in much smaller capacities than regular drives and are quite expensive. So you will have to decide if the cost is worth it.
Flash Drives
Flash Drives are portable drives about the size of your thumb that use flash memory to store data. They replaced floppy disks years ago as the primary method of transporting data from place to place. The early ones only had a capacity of 8 or 16 MB megabytes. Now, storage is in the gigabytes which allows you to store large files such as music and pictures. They connect using a USB interface.
Solid State Drives
Solid State Drives, or SSDs, differ from traditional hard drives in that they contain flash memory rather than a motor, spinning platters, and a read/write head. A big advantage is that you do not have to concern yourself with drive failure due to some mechanical problem, and they require much less power to run.
Like standard drives they come as internal or external, IDE or SATA. Most are 2.5 inches.
A big disadvantage with solid state hard drives, however, is capacity and cost. Presently, most come in much smaller capacities than regular drives and are quite expensive. So you will have to decide if the cost is worth it.
Flash Drives
Flash Drives are portable drives about the size of your thumb that use flash memory to store data. They replaced floppy disks years ago as the primary method of transporting data from place to place. The early ones only had a capacity of 8 or 16 MB megabytes. Now, storage is in the gigabytes which allows you to store large files such as music and pictures. They connect using a USB interface.
Flash Drive