Computer System Basics 2 Hard Drive Storage & File Partitions Computer Forensics BACS 371

Computer System Basics 2  Hardware  Disk Drives Formatting Data Storage File Systems File Partitions

Hardware  Disk Drives  Formatting Low-Level Formatting High-Level Formatting  Data Storage Encoded Bit Byte Word Sector Cluster File

Hard Disk Drives

Hard Disk Drive Sectors and Clusters

Hard Drive Basics  Head  Device which reads and writes data on the disk  Track  Individual circles on disk platter where data are located  Cylinder  A column of tracks on a disk drive with 2 or more platters  Sector  An individual section of data on a track – the smallest amount of data which can be written to the disk – usually 512 bytes  Disk Capacity (CHS calculation) = #cylinders (platters) * #tracks * #sectors

CHS Calculation Example Platter Track Sector Cylinder Capacity = Heads * Tracks * Sectors * Bytes/Sector

Hard Drive Data Storage I  Bit  Binary Digit  Stores either a ‘1’ or a ‘0’  Byte  8 bits  Single ASCII character  Values from 0~255  Word  Usually 4 Bytes  Represents the minimum piece of information which a computer can manipulate  Values from 0~4,294,967,296 Bit Byte Word 32 bits or 4 bytes 8 bits

Hard Drive Data Storage II  Sector  Minimum storage size on a hard drive  One “pie shaped” arc of a platter  Common storage size of 512 Bytes  Established during low-level formatting  Numbered sequentially starting at 1  Cluster (File Allocation Units)  Minimum storage size for a file as determined by file system  Common cluster size is 4096 Bytes (4KB) – 8 Sectors  File  Determined by file system Sectors Clusters File 2 Clusters 8 Sectors * Just an example, your file may occupy more or fewer clusters.

Hard Drive Storage Capacities Name Exact Amount (Bytes) Power of 10 (approx) Power of 2 (Exact) Visual Comparison KilobyteKB Characters – One half page of text MegabyteMB1,048, Small Novel 5MB = Shakespeare’s work GigabyteGB 1,073,741, Truck full of paper TerabyteTB 1,099,511,6 27, TB = Library of Congress PetabytePB 1,125,899,9 06,842,

Formatting and Partitioning  Low-Level Formatting  Physically defines tracks and sectors on disk  Does erase data  Typically only performed at factory  Partitioning  High-Level Formatting  Dividing the disk into volumes – process of defining the file system structure  Appear as logical drives to OS  Does not destroy data on Disk

Partitions To open Computer Management, click Start, and then click Control Panel. Click Performance and Maintenance, click Administrative Tools, and then double-click Computer Management.