Disk Formatting Low Level Formatting Preparing a disk for use Physical Formatting - Low-Level Format - Electronically lays down tracks and sectors on the platter surfaces - Places tracks and sectors on platters - Starting and ending points of all sectors are - Partition Disk marked - Identifies and marks bad sectors - Creates logical disks (volumes) - Writes physical sector addresses - Hard Disk Only - By default, formatting does not wipe disk - High-Level Format - Filling sectors with NULL character 00 is - Creates and initializes file system for option each volume - Low level formatting is performed by manufacturer - Requires special software - Requires many hours for gigabyte drives Low Level Formatting Low Level Formatting Addressing Physical Sectors Addressing Physical Sectors Physical LBA - Address written into sector during low Addressing for HD Floppy Disks Cylinder-Head-Sector (CHS) 2048 512 level formatting Cylinders Count Addresses - Sector address limited by BIOS - Must have before sector can be read Tracks/ 80 0 - 79 Head 2 8 Cylinders - Cylinders can only be numbered 0 to 1023 - If address is corrupted or missing - Heads can only be numbered 0 to 15 52 52 “Sector Not Found” error is given Heads/Sides 2 0 - 1 Sector - Sectors can only be numbered 1 to 63 Cylinder-Head-Sector (CHS) (512, 8, 52) Sectors/ 18 1 - 18 Logical Block Addressing (LBA) Controller reports - Sector address limited by BIOS Blocks CHS - (5, 1, 9) - Converts actual CHS address into a The LBA addressing scheme hides - Cylinders can only be numbered 0 to 1023 logical address acceptable to BIOS Cylinder 5 the physical details of the storage - Heads can only be numbered 0 to 15 Side 1 ('bottom') - Conversion performed by controller device from the BIOS (firmware) - Sectors can only be numbered 1 to 63 Block 9 - Formula varies by manufacturer and BIOS and operating system. Partitioning Disks Partitioning Disks Partitioning Master Boot Record (MBR) - Allows one physical disk to look like - Physical Location multiple logical disks (C:, D:, etc) - Cylinder 0, Side 0, Sector 1 (0, 0, 1) - Logical disks are referred to as volumes - First sector, on the first track, on the first side - Performed by user software - First sector read by BIOS/Firmware - Should be performed before logical - Contains disk information formatting - Number of bytes per sector - Current disk utilities can modify partitions - Total number of sectors per disk on active drives without data loss - Number of sectors per track - Number of heads - Partition Table - If bootable, location of boot volume VBR Partitioning Disks Partitioning Disks Partition Table Partition Table - Specifies disk location and length of each operating system’s partition - Identifies - One Primary Partition - Up to three Extended partitions DOS Partition Table - Partition Table located at (Assumed to be FAT partitions) - Track 0, Side 0, Sector 1 - One partition is set as boot partition All sector addresses reported with LBA - Active Partition - Microsoft Windows - Blessed Partition - Mac OS X Partitioning Disks High Level Formatting Partition Table Logical Formatting GUID Partition Table - Scans the disk for tracks and sectors (Globally Unique Identifier) marked as bad during the low level format - Read only step Logical Sector Numbering - Checks sector header Starts with 0 - Notes these tracks as bad (Physical sectors begin with 1) - "Quick Format" skips this step Sector numbering is consecutive from - Prepares each volume (partition) to hold beginning to end of entire disk data Do not confuse physical and logical - Writes boot record sector numbering - File allocation table (FAT) and copy - Root directory - Data Area High Level Formatting Diskette Formatting Logical Formatting Formatting a floppy diskette - Logical formatting works with clusters - DOS format command Default Cluster Sizes - can perform both low and high level - Allocation block size (logical block size) Size formatting on a floppy disk at the same time - Software addressable group of sectors (in GB) FAT16 FAT32 NTFS HFS+ C:\ > format a: < 0.5 4/8/16 8 2 2 High Level Format - Smallest space to which a file or directory can be saved by operating system 0.5 to 1 32 8 2 4 - Default - no files placed on disk C:\ > format a: /s - Clusters are logical addresses for data 1 to 2 64 8 4 8 - With /s switch stored in the Data Area 2 to 8 8 8 8 - System files will be placed on the disk C:\ > format a: /u 8 to 16 16 8 8 - Number of sectors per disk size varies - Creates a bootable floppy based on file system and partition size 16 to 32 32 8 8 Low level format > 32 64 8 8 - Floppy diskette clusters have either one - Use /u switch or two sectors per cluster - Overwrites data area of disk (wipe).