Hard Drive

HARD DRIVES

The hard disk drive or hard drive is the main location where all data is stored. Most hard disk drives consist of spinning platters of aluminum, glass or ceramic that are coated with a magnetic media.
A single hard disk usually consists of several platters. Each platter requires two read/write heads, one for each side. All the read/write heads are attached to a single access arm so that they cannot move independently. Each platter has the same number of tracks, and a track location that cuts across all platters is called a cylinder. For example, a typical 84mb hard disk for a PC might have two platters (four sides) and 1,053 cylinders.

Hard drive manufacturers: fujitsu, ibm/hitachi, maxtor, seagate, western digital

Tips for buying a hard drive

1. You should make sure there's space in the case for another drive. Most desktop PC cases have at least one, and sometimes several spaces, internal drive bays--places where you can mount extra hard drives. But check your manual and open up the case. Some of the smaller low-profile computer cases don't have room for additional internal hard drives, so you won't be able to use both the your old and a new drive in the same computer case. In which case you will need to buy an external hard drive.

2. Capacity typical hard drives are about 100GB they can go up to 1 TB the more information such as pictures, files, music and videos your going to store the more space your going to need.

3. RPM rotation per minute The best is 15,000 rpm however you should consider buying a hard drive with a fast rotational speed of 7,200 revolutions per minute (rpm) or higher. You should expect to spend less for a slower 5,400-rpm hard drive.

4. Seek Time you should look for an average seek time of fewer than 4.7 milliseconds (ms), and a data transfer rate of at least 15 megabytes (MB) per second. The actual sustained speed of the drive will be less than the maximum "burst" speed.

7. Buffer 8MB or better: When a system requests data, a hard drive will not only fetch what is requested, but it will also load its buffer memory with extra information that the processor is likely to ask for next. While a 2MB buffer is good, that's plenty of room to keep the data flowing, I found that drives with 8MB performed is best! for disk-intensive tasks.

8. Transfer Speed:

Internal Hard Drives

Parallel ATA 33, 66, 100, 133MB/s
Serial ATA 150-300MB/s
SCSI 33-640MB/s

External Hard Drives

Serial ATA 150-300MB/s
USB 12Mbps up to 480Mbps
Firewire 400Mbps up to 800Mbps
SCSI 33-640MB/s

9. External Hard Drives. External drives is a good idea if you need to lock up important data or you need to transport a lot of data to another PC. Note external hard drives cost quite a bit more than internal drives and usually require an FireWire or USB 2.0 interface.

10. There are three main types of internal hard drive Parallel ATA, Serial ATA and SCSI.

Below is a picture of what the inside of the hard disk drive looks like. The Hard disk drive has four main components. The head actuator controls the head arm, which reads the information off of the disk platter. The chassis encases and holds all the hard disk drive components.

Platter - The actual fixed disk within the hard disk drive. There can be several platters within the hard drive
Heads - Each side of a platter
Tracks - Large sections that completely circle the platter
Sector - Section on the track
Cluster - Smallest unit of measurement that a hard drive will read
Cylinder - Tracks of the same diameter on each platter

Types of Hard Drives

IDE Abbreviation of either Intelligent Drive Electronics or Integrated Drive Electronics, depending on who you ask. An IDE interface is an interface for mass storage devices in which the controller is integrated into the disk or CD-ROM drive. IDE usually contains one controller and 40 pins where you can install up to only 2 devices a typical speed of an IDE drives is about 3/MBs

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EIDE Short for Enhanced IDE, a newer version of the IDE mass storage device interface standard developed by Western Digital Corporation. It supports data rates of between 4 and 16.6 MBps, about three to four times faster than the old IDE standard. In addition, it can support mass storage devices of up to 8.4 gigabytes, whereas the old standard was limited to 528 MB. Because of its lower cost, enhanced EIDE has replaced SCSI in many areas.

ATA: Known also as IDE, supports one or two hard drives, a 16-bit interface and PIO modes 0, 1 and 2.

ATA-2: Supports faster PIO modes (3 and 4) and multiword DMA modes (1 and 2). Also supports logical block addressing (LBA) and block transfers. ATA-2 is marketed as Fast ATA and Enhanced IDE (EIDE). Also known as Ultra- DMA/0

ATA/33: Also called Ultra-DMA/2 , and DMA-33, supports multiword DMA mode 3 running at 33 MBps.

ATA/66: or Ultra-DMA/4 A new version of ATA proposed by Quantum Corporation, and supported by Intel, that will double ATA's throughput to 66 MBps. Other ATA supports speeds of 100 and 133MB/s

ATA/100 aka Ultra-DMA/5

ATA/133 aka Ultra-DMA/6 currently the fastest IDE hard drive in the market

Note if you do choose to have a hard drive that supports 66MB/s and higher you will need to use an 80pin ribbon cable instead of the traditional 40pin ribbon cable which only supports 33MB/s.

Hard Drive Geometry

LBA Short for logical block addressing, a method used with SCSI and IDE disk drives to translate the cylinder, head, and sector specifications of the drive into addresses that can be used by an enhanced BIOS. LBA is used with drive's that are larger than 504MB.

1,024 cyl * 16 heads * 63 sectors/track * 512 bytes/sector = 504MB

CHS Short for Cylinders, Heads and Sector translation

E/CHS Extended CHS a competitior to LBA supports different translation

1,024 cyl * 256 heads * 63 sectors/track * 512 bytes/sector = 8.4GB

INT/13 Interrupt 13 extensions developed by Phoenix technology to support up to 137GB

Best when installing hard drives it is best to set it to AUTO detect mode in the CMOS/BIOS setup

Hard drive maintenance

DEFRAG A DOS and Windows utility that defragments your hard disk. In Windows 95, you run Defrag by selecting Start->Programs->Accessories->System Tools->Disk Defragmenter.

SCANDISK A DOS and Windows utility that finds different types of errors on hard disks and is able to correct some of them. In DOS, you run Scandisk by entering scandisk at the prompt and pressing the Enter key. In Windows 95, you can run Scandisk by selecting Start->Programs->Accessories->System Tools->Scandisk.
Among other things, Scandisk checks the disk platters for defects and also looks for lost clusters that are sometimes created when a program aborts.

In Windows 2K/XP go to start>run>cmd and type CHKDSK from the command prompt

File systems

FAT or File Allocation Table A table that the operating system uses to locate files on a disk. Due to fragmentation, a file may be divided into many sections that are scattered around the disk. The FAT keeps track of all these pieces.
In DOS systems, FATs are stored in hidden files, called FAT files .
The FAT system for older versions of Windows 95 is called VFAT, and the one for new versions of Windows 95 and Windows 98 is called FAT32. A new version of the file allocation table (FAT) available in Windows 95 OSR 2 and Windows 98. FAT32 increases the number of bits used to address clusters and also reduces the size of each cluster. The result is that it can support larger disks (up to 2 terabytes) and better storage efficiency (less slack space).

NTFS-New technology file system use in Windows 2K/XP/NT environment for security support

Steps in installing a hard drive

1. Buy a hard drive usually look for space in terms of GB example a 40 GB hard drive, the RPM/s usually 7200 or more is the revolution per minute and the speed of the hard drive EIDE vs. Ultra DMA/33 which is faster. Several vendors to consider when buying a hard drive include Maxtor, Seagate, IBM, Western Digital, Fujitsu and Quantum.

2. Back up your computer and record settings like CMOS and desktop settings before installing the hard drive.

3. Set jumper settings of master and slave, example if one hard drive and CD/ROM were daisy chained on one 40-pin ribbon cable then the jumper settings would be master on the hard drive and slave on the CD/ROM. You can set jumper settings by looking at the back of the hard drive and CD/ROM and follow the master and slave specification

4. Install 40 pin ribbon cable to hard drive making sure pin one which is the red section is closest to the Molex power connector and install other side to IDE controllers.

5. Install the Molex power connector from power supply to hard drive for power if it's a PATA if a SATA hard drive install the 15 pin black power connector.

6.Go to CMOS setup and configure hard drives using the AUTO detect or manual configuration

7. Partition hard drive, which is dividing hard drive into sections. You can either use the DOS utility FDISK or use a 3rd party software like PQ Magic to partition your drive. Usually the first partition is the Primary partition. Set it to active in order for the OS to boot up. That which is left over on the hard drive will become the extended partition. Finally, divide the extended partition into logical partitions.
Example: if the hard drive has total space of 4GB, the primary partition under FAT16 will be 2GB, which is the most you can allocate per hard drive. The left over is the extended partition, which is 2GB. To get this figure, Subtract 4GB total space minus the 2GB max in FAT16 and you have 2GB left. Then divide the extended partition to logical partition, in this case we will divide by 2, which leaves 1GB of D drive and 1GB of E drive. Under FAT32 large disk support is enabled and can partition hard drives into the highest number so if you have a 40GB hard drive you can partition that to the full 40GB max.

8. High-level Format each partition drive. This will make your partition usable.

9. Install a file system FAT16, FAT32 and NTFS, the latter being used for security with the drives.

10. Install and load the Operating System