1. Implementing Hard Drives Chapter 10

2. Overview In this chapter, you will learn to
Explain the partitions available in Windows
Discuss the formatting options
Partition and format a hard drive
Instructor Tip
When gaining attention and establishing common ground, ask questions to the class such as, “Who here has ever partitioned or formatted a hard drive?” or “Who here has ever had a hard drive crash?”
For a positive statement, tell the class, “In this lesson, we are going to learn how to set up a hard drive, partition and format it, and use tools to maintain and troubleshoot a hard drive.”

3. Introduction 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.

4. Partitioning
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: or D:
Logical divisions of a hard drive.

5. Partitioning

6. Formatting 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.

7. Hard Drive Partitions
Partitions provides flexibility in HD organization. You can organize a drive in a way that suits your taste. How?
Partitioning enables a single HD to store more than one operating system .
Windows 2000/XP support 2 different Partitioning methods:
Master Boot Record (MBR) partitioning scheme.
Older but universal
The HD is called ‘basic disk’
Dynamic partitioning scheme.
Newer but proprietary to Microsoft
The HD is called ‘dynamic disk’.

8. Basic Disk
Basic disk partitioning creates two very small data structures on a drive:
Master Boot Record (MBR)
and a Partition Table
Stores them on the first sector of the HD- called the Boot 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.

9. Basic Disk
MBR looks in the partition table for a partition with a valid operating system.
Only one MBR per disk
Program
Data

10. Basic Disk Partition table supports up to 4 partitions.
Supports 2 types of partitions: primary and extended.
Primary: designed to support operating systems.(bootable)
Extended: not bootable
A 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)

11. Basic Disk
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.

12. Hard Drive PartitioningC: ?

13. Volume boot sector
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.

14. Primary Partition Can be bootable
Has 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. Boot Sector

16. Boot Sector 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?

17. Extended Partition 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 Active
Completely optional. What doest means?
Why we try to create extended partition.

18. Partitions Primary Partition Extended Partition Logical Drive 1
Drive Letter = c:
Drive Letter = d:
Set to “Active”
Stores O.S.
Logical
Drive 2
Drive Letter = e:
Hard Disk

19. Example 2 Drives (DOS) Dual OS Master Primary Partition
Extended Partition C: E: F:
MBR
tells layout of the disk
Logical Drives
Slave
Primary Partition
Extended Partition D: G: H:
MBR
tells layout of the disk
Logical Drives

20. When to partition 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. Hard Drive Formatting Done after partitioning
Every 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
FAT32
NTFS.
Root directory provides foundation upon which OS builds files and folders.

23. FAT – File Allocation Table
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 16 bits. Therefore there are 64K sectors (2^16).
64K sectors limits partition size to 32MB (how?)

24. FAT – File Allocation Table
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
FFF7
0001
0002
……….
FFFF

25. FAT Limited 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

26. Clustering
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. Clustering
Number of clusters is still 64K (16 bit). So, number of sectors/cluster is determined according to partition size. (how?)
The large the partition the more sector per cluster.

28. Clusters and Sectors

29. FAT16
FAT16: clustering FAT where the cluster is represented in 16 bits.
Cluster sizes: 4,8,16,32 64 (max. partition is 2GB). 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.

30. FAT16 in Action When an API tells the OS to save a file (MOM.TXT).
Windows start at beginning of FAT looking for the first open cluster.

31. FAT16 in Action
Before filling 3ABC window enter the value 3ABC in 3ABB status.
FAT 16

32. FAT16 in Action

33. FAT16 in Action
0000 = Good FFF7 = Bad FFFF = End of File

34. FAT and Root Directory
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?

35. Fragmentation
Fragmentation occurs when files are spread across drives (not contiguous)
Individual files are broken into pieces that fit into a sector or cluster
The pieces are stored on the hard drive but may not be stored in contiguous clusters
Fragment 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

38. FAT 32 Uses 32 bits to describe each cluster
Cluster 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

39. NTFS 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.

40. NTFS
Security:
Provides file and folder access control
Uses Access Control List with
permissions
If 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. (Slower).
Encrypting file system:
Allows files and folders to be
encrypted and unreadable to
anyone without the key

41. NTFS Files and folders can be encrypted or compressed Disk quotas
Can control how users can
use space
Set on a per-drive basis
Cluster sizes
Can adjust cluster sizes
Rare to do so

42. Divisions of a Hard Drive

43. Partitioning and Formatting Process

44. Bootable Disks
Any software that can boot up a system is by default OS.
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

45. Install Hard Drive
Connectivity
CMOS
Partitioning
Formatting