CHAPTER 7 Storage 3.ppt

1、CHAPTER 7 Storage,Hard Disks,Hard Disks,Low-level format- organizes both sides of each platter into tracks and sectors to define where items will be stored on the disk. Partitioning: divide hard disk into separate areas called partitions; each partition functions as if it were a separate hard disk d

2、rive. High-level format defines the file allocation table (FAT) for each partition, which is a table of information used to locate files on the disk.,Hard Disks,Use thicker, metallic platters for storage Faster than a floppy diskette Large capacity Sensitive instruments,Low Level Formatting,Low leve

3、l format scans disk for defects and sets aside sectors with defects so they are not used for data. IDE drives should never be low level formatted by a user or technician. Only high level format necessary.,Hard Drive,Floppies,Two sizes 3.5 inch 5.25 inch 3.5 inch holds 1.44 MB for High density and 75

4、0 KB for Double Density Connected with 34 pin ribbon cable Two Floppy Drives possible Has twist in cable to distinguish A drive from B drive,SCSI,Pronounced Scuzzy Small Computer Systems Interface For wide range of peripheral devices, including hard disks, tape drives, optical drives, CD-ROMs and di

5、sk arrays. 8 devices can connect to a daisy chain This chain must be terminated at both ends Each device on chain is assigned unique device ID number that is determined by jumpers or DIP switches,Installing and configuring SCSI,SCSI bus supports 8 devices There are eight SCSI IDs numbered 0 through

6、7 ID 7 is always reserved for the SCSI host adapter SCSI hard disk, if used as a boot drive, is assigned SCSI ID 0 If you have both IDE and SCSI hard drive, IDE drive should be boot drive,Types of SCSIs,SCSI 1- 5 MB transfer rate, Centronics 50 pin or DB 25, has 8 bit bus SCSI 2 -also SCSI Fast Wide

7、, includes 16 bit bus , called Wide SCSI, and twice as fast transfer rate SCSI 3- Includes Ultra SCSI, Wide Ultra SCSI, and Ultra 2 SCSI, 16 bit bus with up to 80 MBps transfer rate,RAID,Redundant Array of Independent Disks Category of disk drives that employs 2 or more drives in combination for fau

8、lt tolerance (error recovery) 10 levels of RAID 3 on test will be: RAID 0, RAID 3, RAID 5,RAID continued,RAID 0- Striped disk without parity RAID 3- Parallel transfer with parity RAID 5- Data striping with parity,How Data is Organized on Disk,Tracks- circular areas of the disk Length of a track one

9、circumference of disk Over 1000 on a hard disk Data first written to outer most track Sectors- Divides tracks sections On a floppy 9 sectors exits Cylinders- Logical groupings of the the same track on each disk surface in a disk unit Clusters- Groups of sectors used by operating system 64 sectors in

10、 one cluster,Track= concentric circle,Sector = small arc of track,Can store 512 bytes,Tracks and sectors,Interleaving,Allows the read/write head to use the rotation of the disk to its advantage One sector is written to and the disk skips to several sectors down,Formatting,Low level formatting done a

11、t factory Builds the File Allocation Table (FAT) Physically scans the disk media for defects Remember FAT is always located at Track 0 High level formatting is automatically done during installation of operating system,Operating System File Systems,DOS uses FAT Windows 3.x uses Virtual FAT Win 95 uses VFAT and FAT32 Win NT uses NTFS,Backing up data,Archival: full backup- contains everything from the hard disk Incremental: contains only files that have be