1

OverviewIn this chapter, you will learn to

Explain the partitions available in Windows

Discuss the formatting options

Partition and format a hard drive

Introduction

3

A new Hdive (HD) is nothing than a huge pile of sectors.

CMOS sees the drive, it shows up in the auto-detect screen and BIOS knows how to talk to drive.

For operating system, It must organize that pile of sectors so one can create 2 things: folders and files.

After installing a HD, 2 more steps must be performed to translate a drives geometry into something usable to the system. Partitioning and formatting.

Partitioning

4

Process of electronically subdividing the physical hard drive into groups of cylinders. Called partitions or volumes A HD must have at least one partition. You can have multiple partitions on single HD.Windows assigns them names such as C:C: or D:D:LogicalLogical divisions of a hard drive.

Partitioning

5

Formatting

6

After partition you must format derive.

Installs a file system onto the drive that organizes each partition in such a way that operating system can store files and folders on the drive. called high level formatting.

Hard Drive Partitions

7

Partitions provides flexibility in HD organization. You can organize a drive in a way that suits your taste. How?How?

Partitioning enables a single HD to store more than one operating system .

Windows 2000/XP support 2 different Partitioning methodsPartitioning methods: 1.1. MMaster BBoot RRecord (MBRMBR) partitioning

scheme. • Older but universal• The HD is called ‘basic disk’

2.2. DynamicDynamic partitioning scheme.• Newer but proprietary to Microsoft• The HD is called ‘dynamic disk’.

Basic Disk

8

Basic disk partitioning creates two very small data structures on a drive: Master Boot Record (MBR) and a Partition TableStores them on the first sector of the

HD- called the Boot SectorBoot Sector.MBR is a tiny bit of code that takes

control of the boot process from system BIOS.

When a computer boots to a HD, BIOS automatically looks for MBR code on the boot sector.

Basic Disk

9

MBR looks in the partition table for a partition with a valid operating system.

Only one MBR per disk

Program Data

Basic Disk

10

Partition table supports up to 4 partitions.Supports 2 types of partitions: primary and

extended.Primary: designed to support operating

systems.(bootable) Extended: not bootableA single disk may have up to 3 primary

partitions and only one extended partition.If you don’t have an extended partition, you

may have up to 4 primary partitions. This allows for multiple (up to 4) operating systems (called multiboot, dual boot)

Basic Disk

11

Each partition must have some unique identifier to enable user to recognize it as an individual partition.

Windows assign primary partitions a drive letter from C: to Z:. Extended partition do not get drive letters.

After you create an extend partition you must create logical drives within that extend partition. Logical drive get a drive letter from D: to Z:

C: is always reserved for first primary partition in windows PC.

Hard Drive Partitioning

12

C:

?

Volume boot sector

13

The first sector of the first cylinder of each partition also has a boot sector called volume boot sector.

Stores information important to its partition, such as location of OS boot files and partition size.

Primary Partition

14

Can be bootableHas a special setting called ‘active’ stored

in the partition table. It is either on/off on each primary partition.

Only one partition at a time can be the active partition because you can run only one OS at a time.

At boot, the MBR uses the active setting to determine which primary partition is active to load OS from.

The partition is set active when you install OS. It never actually says this in the install.

Rest of chapter assume only one primary partition.

15

16

Few system use more than one primary partition.

You almost never see four partitions used in windows world.

How we can change active partition? And why?

Extended Partition

17

Why we have extended partition?Further divided into logical drives which

get a drive letter from D: to Z:An extend partition may have as many

logical drives as you wish.

Cannot be bootable or ActiveCompletely optional. What doest means?Why we try to create extended partition.

18

Primary Partition

Drive Letter = c:

Set to “Active”

Stores O.S.

Extended Partition

LogicalDrive 1

LogicalDrive 2

Primary Partition

Hard Disk

Drive Letter = d:

Drive Letter = e:

19

MBRtells layout of the disk

Primary Partition Extended Partition

Logical Drives

C: E: F:

MBRtells layout of the disk

Primary Partition Extended Partition

Logical Drives

D: G: H:

Master

Slave

2 Drives (DOS)2 Drives (DOS)Dual OSDual OS

When to partition

20

Two most common situations:when installing an OS on a new system when adding a second drive to an

existing system Traditionally, once a partition is made,

you can not change its size or type other than by erasing it.

Third-party tools can non-destructively resize partitions (without losing the data)

Windows 2000 and XP can non-destructively resize a partition to be larger but not smaller.

Vista can non-destructively resize partitions any way we wish.

21

Hard Drive Formatting

22

Done after partitioningEvery partition needs to be formatted.

Why?Formatting does two things

It creates a file system – like a library’s card catalog

and makes the root directory in that file system.

Current file systems in Windows: FAT16 FAT32NTFS.

Root directory provides foundation upon which OS builds files and folders.

FAT – File Allocation Table

23

A file is stored in many sectors (possibly one).

The main job of FAT is to track which sectors are assigned to each file, which sectors are unused and which are bad.

The sector number is represented in 1616 bits. Therefore there are 64K sectors (2^16).

64K sectors limits partition size to 32MB (how?)

FAT – File Allocation Table

24

The right column of the FAT contains information about the status of sectors.

Formatting: creating FAT and testing sectors. Assign 0000 to good and open for use sectors and FFF7 to bad ones.OS must locate bad sectors (if any). This mapping of bad sectors is one of the functions of high-level formatting.Floppy disks use FAT with 12 bits.

0000 0000

0001 FFF7

0002 0000

…….…

0000

…….…

0000

FFFF

0000

FAT Limited

25

Using 16-bit FAT addresses a maximum of 64 K location.

The size of hard disk partition should be limited to 64 K x 512 bytes per sector (32 M).

As hard drives grew in size you could use FDISK to break them up into multiple partitions.

Therefore using FAT 16 with very large HD is unacceptable.

Solution was clustering, allowing partition sizes up to 2 GB

Clustering

26

To break the limit of 32MB in partition size with backward compatibility.

Enables one to format partition larger than 32MB

Idea: combining a set of contiguous sectors and treating them as a single unit (cluster) in FAT. i.e. FAT addresses a cluster instead of a sector. So, the cluster became the smallest addressable block of data stored on a drive. The size of a cluster is not fixed.

27

Number of clusters is still 64K (16 bit). So, number of sectors/cluster is determined according to partition size. (how?how?)

The large the partition the more sector per cluster.

Clustering

28

FAT16

29

FAT16: clustering FAT where the cluster is represented in 16 bits.

Cluster sizes: 4,8,16,32 64 (max. partition is 2GB). Compute it?Compute it?

Hard Drives become fragmented. This mean that data for one individual file may not be in consecutive clusters

Excess fragmentation slows down systems. It needs defragmentation from time to time.

FAT16 in Action

30

When an API tells the OS to save a file (MOM.TXT).

Windows start at beginning of FAT looking for the first open cluster.

FAT16 in Action

31

FAT 16

Before filling 3ABC window enter the value 3ABC in 3ABB status.

FAT16 in Action

32

FAT16 in Action

330000 = Good FFF7 = Bad FFFF = End of File

34

Windows then goes to the folder storing the file and adds the file name and the cluster’s number to the folder list

File folder located in different cluster.What happen if program requesting that

file?

Fragmentation

35

Fragmentation occurs when files are spread across drives (not contiguous)Individual files are broken into pieces that fit

into a sector or clusterThe pieces are stored on the hard drive but

may not be stored in contiguous clustersFragment take place all the time on FAT 16.

Fragmentation slows down the system during hard drive reads and writes

Programs such as Disk Defragmenter or Speed Disk can be used to defragment files, folders, or both

Takes longer for system to piece together and can impact performance.

36

Disk Defragmenter

37

Disk Defragmenter

FAT 32

38

Uses 32 bits to describe each clusterCluster size can drop to reasonable size

compared to FAT16.A 2-GB volume using FAT16 would use 32-

KB clusters, while the same 2-GB volume using FAT32 would use the minimum cluster size (4KB).

FAT 32 support partition up to 2 terabyte.But needs de-fragmentation

Remember, only DOS and Windows 3.x/95/98/Me use FAT

NTFS

39

File system of choice today.NT File System (NT came from Windows

NT, first OS to use it)Windows NT, 2000, XP, Vista.Uses clusters and file allocation table in a

much more complex and powerful way compared to FAT16 and FAT32 this table called Master File Table (MFT).

Main improvements: redundancy, security, compression, encryption, disk quotas, and cluster sizing.

NTFS

40

Security:Provides file and folder access controlUses Access Control List Access Control List with permissionspermissionsIf you’re on the list, you’re granted the specific permission

Compression: Compresses data on a hard drive to allow more data to be written to the drive. (SlowerSlower).

Encrypting file system:Allows files and folders to be encrypted and unreadable to anyone without the key

NTFS

41

Files and folders can be encrypted or compressed

Disk quotasCan control how users

can use spaceSet on a per-drive

basis

Cluster sizesCan adjust cluster

sizesRare to do so

Divisions of a Hard Drive

42

43

Bootable Disks

44

Any softwaresoftware that can boot up a system is by default OS.

Bootable disk Bootable disk is any removable media that has a bootable OS installed

Floppy, CD-ROM, USB thumb drive

All Windows and Linux installation CDs are bootable

Install Hard Drive

45

ConnectivityCMOSPartitioningFormatting

46

48

49

50

51

52

53

54