Hard Drive

Drive Capacity MeasurementContainsUsually Used for Measuring Size Of KB (kilobytes 1,024 bytesFloppy drives MB (megabytes)1,024 KBDCs, small hard drives, cartridge drives, small tape drives GB (gigabytes1,024 MB Hard drives, large capacity cartridge drives, some tape drives, and DVDs TB (terabytes)1,024 GBVery large hard drives and some tape drives

Hard Drive Architecture Voice coil actuator Read/write heads Spindle Platters Side 0 Side 1 (underside) Side 1 (underside) Side 2 Side 3 (underside) Side 3 (underside) Actuator arms

Disk Drive Geometry Track Sector Cylinder

Traditional Sectors

Zoned-Bit Recording Sectors

Sector Interleave

How Hard Drives Work 7200 RPM Head

Form Factor 3.5-inch drive 5.25-inch drive

IDE Hard Drive IDE data cable Red stripe indicates Pin 1 Red stripe indicates Pin 1 Jumpers to specify master, slave, or cable select Power cable

Primary and Secondary IDE Drives Motherboard Set as slave DVD drive CD-RW drive Set as master HD0 boot drive Set as a slave HD1 second hard drive Secondary IDE Primary IDE

Connect IDE Drives to the Cable Connect to master Connect to slave or single

Ultra DMA Drives  An extension of the ATA disk interface  Transfer rates of 33, 66, or 100 MBps  Backward compatible with EIDE system boards and controllers (but speed limited to 16.6 MBps)

Partitioning A partition is an isolated section of a disk that functions like a separate physical drive. Partitions enable you to create a logical disk structure to organize hard drives.

Formatting Formatting is a system function that prepares a mass storage medium to hold data. Each partition on a drive is formatted separately.

SCSI Chain HBA Internal drive External tape drive External tape drive External CD-ROM drive External CD-ROM drive

SCSI Device IDs By switch By jumper

SCSI Binary Jumper Settings

TechniqueDescription Single-Ended (SE) Uses a single wire for each bit of data. Cable length is limited to 6 meters due to noise. High Voltage Differential (HVD) Signaling Also known as differential signaling. Uses two wires for each data bit—one for the actual data and one for the inverse of the data. By comparing the data and its inverse, noise can be identified and rejected. Cable length can be up to 25 meters. Connecting an HVD device in an SE chain damages SE devices and sometimes also the HVD devices. Low Voltage Differential (LVD) Signaling Uses less power than HVD devices and can be chained with SE devices without damaging any devices. An LVD device on an SE chain will function like an SE device, so you lose the advantages of differential signaling. LVD cabling is limited to 12 meters. SCSI Signaling Techniques

SCSI Termination SCSI chain termination By terminating resistor By switch By jumper

SCSI TypeDescription SCSI-1 (narrow SCSI or regular SCSI) 8 bits wide. Supports up to 8 devices (7 plus the HBA). Uses a 50-pin connector; transfers data at up to 5 MB per second. Wide SCSI 16 bits wide. Supports up to 16 devices (15 plus the HBA). Transfers data at up to 20 MB per second. Ultra Wide SCSI 16 bits wide. The 50-pin (or lower) connections carry one byte at a time. Ultra Wide connections carry two bytes at a time. Transfers data at up to 40 MB per second. Fast SCSI8 bits wide. Transfers data at up to 10 MB per second. Fast Wide SCSI16 bits wide. Transfers data at up to 20 MB per second. Ultra SCSI 16 bits wide. Transfers data at up to 40 MB per second. If implemented on an 8-bit bus, data is transferred at up to 20 MB per second. Ultra2 SCSI 16 bits wide. Transfers data at up to 80 MB per second. If implemented on an 8-bit bus, data is transferred at up to 40 MB per second. Ultra3 SCSI 16 bits wide. Transfers data at up to 160 MB per second. If implemented on an 8-bit bus, data is transferred at up to 80 MB per second. Ultra 320 SCSI 16 bits wide. Transfers data at up to 320 MB per second. If implemented on an 8-bit bus, data is transferred at up to 160 MB per second. SCSI Types

External SCSI Connectors SCSI 1 External A SCSI DB 25 SCSI 2 External A

Internal SCSI Connectors HBA is installed in the computer Connector on HBA to internal SCSI flat cable Connector from SCSI flat cable to SCSI drive

SymptomPossible ProblemSolution Error message at boot Drive Not Ready-System Halted Drive is damaged. Drive is not configured for Master or Cable Select as appropriate to the system. Data cable is not connected or incorrectly connected to the drive. Visually inspect the drive and its connections; correct as needed. POST error codes in the 17xx range 1701: Drive not found. 1702: Hard drive adapter not found. 1703: Hard drive failure. 1704: Hard drive or adapter failure. 1780, 1790: Hard drive 0 failed. 1781, 1791: Hard drive 1 failed. 1782: Hard drive controller failed. Visually inspect connections and reconnect drive. Replace failed component. Common Problems with Hard Drives

SymptomPossible ProblemSolution Can’t read from or write to the drive Bad sectors on the drive. IRQ conflicts. Drive failure. Virus attack. Run Scandisk to try to recover information from bad sectors and to mark those sectors as unusable. Check Device Manager for hardware resource conflicts and for indications of drive failure. Run virus check software and remove any viruses found. System will not boot Drive disconnected, damaged, or not recognized by the BIOS. Visually inspect and reconnect drive. Enable drive in CMOS setup utility. Drive is making grinding noises that keep repeating in a regular pattern Physically damaged drive, most likely due to a head crash. Replace the hard drive. Remind users and technicians not to move a machine while it is in use since that is the most common cause of head crashes. Data is frequently being corrupted or utilities are not running properly System not being shut down properly; drive is in the process of failing; virus. Educate users on how to properly shut down the system. Run virus protection software. Back up the data. Replace failed or failing drive. Common Problems with Hard Drives (Cont.)

IDE Drive Troubleshooting  If you have one drive on a channel, it must be configured as single—not master or slave.  With two drives on a channel, set both to cable select or configure them both manually, setting one to master and the other to slave.  If you remove the second IDE hard disk from a computer with two IDE drives installed, verify that the disk that remains in the computer is set as single.  If you need to move an IDE drive from one computer to another, you likely won't run into problems.

SCSI Drive Troubleshooting  Most problems with SCSI disks are due to incorrect ID settings and improper termination.  When a SCSI system is booted or reset, SCSI controllers generally need to renew all SCSI device connections before activating the devices, causing a delay during POST.  SCSI cables should be handled carefully to minimize problems.  If you intend for a SCSI disk to be bootable after you install it, you must enable the SCSI BIOS.  Verify that all SCSI devices have unique SCSI ID numbers.  When installing an additional SCSI hard drive into a computer where only one connector is available on the SCSI cable and the cable itself is terminated, remove and replace the cable with one that has multiple connectors.

Slow Drives  Drive is too full—Windows needs free drive space to write temporary and swap files.  Fragmentation—Run a disk defragmenter program monthly to clean up defragmentation and put files in contiguous blocks.  Controller too slow—If you have a fast drive connected to a slower controller, the drive will transfer data at the slower rate.  The wrong cable is used—If you use a cable for a slower drive, it can result in decreased performance.

UtilityDescriptionSyntax chkdsk Enables you to check the hard disk for errors. If any errors are reported, you can then use other tools such as ScanDisk to repair those errors. At a command prompt, enter chkdsk drive letter. For example, to check the C drive, enter chkdsk C:. Disk Defragmenter (Defrag.exe) Rearranges the files on your computer's hard disk to make them contiguous. Use Disk Defragmenter when a hard disk's performance has slowed down. Choose Start→All Programs→Accessories→System Tools→Disk Defragmenter, or choose Start→Run and enter defrag in the Open text box. Disk Management Windows XP's graphical tool for managing drives and partitions. From the Start menu, right-click My Computer and choose Manage. Select Disk Management in the Computer Management window. Fdisk.exe and Format.exe DOS-based disk and file- management tools; Fdisk is for disk partitioning and Format is for formatting. Boot with a bootable DOS floppy disk containing the utilities and run them at the command prompt. Scandisk (Scandisk.exe) Scans and repairs problems with your computer's hard disk. Choose Start→All Programs→Accessories→System Tools→ScanDisk, or choose Start→Run and enter scandisk in the Open text box. Hard Drive Maintenance Tools

Striping with RAID Level 0 Data is divided across all drives. DDAATTAA DATA

RAID Level 1 Mirroring Drive 0Drive 1 Duplexing Drive 0Drive 1 DATADATA DATA DATADATADATADATADATADATA

RAID Level 5 DD DD DD DD ParityParity ParityParity AA DD AA AA ParityParity TT AA AA TT ParityParity AA TT TT TT ParityParity AA AA AA AA DATA