File and Disk
Maintenance
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File Systems
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A file system defines the structure and the
rules used to read, write, and maintain
information stored on a disk.
Which system used is determined by;
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Hardware
Software
Security needs
Need for a dual-booting system
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FAT???
file allocation table – where the OS
records how the disk space is used
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File Systems
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FAT 16 – oldest, created for DOS, supported by
most OSs’, cannot be installed on partitions larger
than 2 GB, or on hard drives larger than 4GB.
FAT 32 – supports disks from 512 to 2TB,
compatible with Windows 98 and up
NTFS – (new technology file system) – better file
security (Encrypting File System), disk
compression, logging features, reliability and
stability. NTFS volumes can not be accessed by
DOS, or Windows 95 or Windows 98.
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File Systems
The operating system keeps track of data
(documents, pictures, etc.) by placing it into a file.
To store and retrieve files:
 Disk divided into tracks
Tracks are divided into sectors
 Sectors grouped into clusters
Number of sectors in a cluster is determined by
Size of the hard drive
File allocation system – FAT, FAT32, NTFS, e
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When you format a disk the operating systems
creates concentric recording bands, called tracks,
around the circumference of the disk. Then, the
formatting program (in our case Windows XP)
subdivides each track into equal parts, called
sectors. Although not all of them are shown in
the following diagram, there are 80 concentric
tracks on a 3 ½ inch high density diskette and
each track is divided into 18 sectors. Each sector
in turn contains 512 bytes.
So let’s see . . . . . 80 tracks X 18 sectors X 2
sides X 512 bytes = 1,474,560 bytes = 1.4 MB
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Tracks
Sectors
within a
Track
Cluster
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A hard disk has extremely smooth metal or glass plates
called “platters” (vs. the floppy mylar disk of a floppy disk).
Each platter is divided into tracks and sectors by the format
operation, like a floppy disk, however the number of tracks
and sectors is different. The number of tracks on a hard
disk depends on the disk size and the manufacturer.
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Clusters?
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A cluster, also known as an allocation unit, consists of
one or more sectors of storage space, and represents the
minimum amount of space that an operating system
allocates when saving the contents of a file to a disk.
The number of sectors per cluster is dependent on
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Type of disk (floppy disk, hard disk)
Version of operating systems
Size of disk
Every sector contains 512 bytes. (NTFS does allow you to
change this number.)
The number of clusters per disk is determined by the
filing system (FAT 16, FAT 32 or NTFS).
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DRIVE SIZE
FAT 16
Cluster Size
FAT 32
Cluster Size
NTFS
Cluster Size
260 to 511 MB
8 KB (16 sectors)
Not Supported
512 bytes (1 sector)
512 to 1023 MB
16 KB (32 sectors)
4 KB (8 sectors)
1KB (2 sectors)
1024 MB to 2 GB
32 KB (64 sectors)
4 KB (8 sectors)
2 KB (4 sectors)
2 to 4 GB
64 KB (128 sectors)
4 KB (8 sectors)
4 KB (8 sectors)
4 to 8 GB
Not Supported
4 KB (8 sectors)
8 KB (16 sectors)
8 to 16 GB
Not Supported
8 KB (16 sectors)
16 KB (32 sectors)
16 to 32 GB
Not Supported
16 KB (32 sectors)
32 KB ( 64 sectors)
>32 GB (up to 2 TB)
Not Supported
32 KB (64 sectors)
64 KB (128 sectors)
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Example - File size = 2KB
Hard drive = 2GB
 FAT 16 – the file will use 1 cluster which is 64 sectors, so
 64 X 512 bytes per sector = 32KB – 2KB = 30KB slack
space
 FAT 32 – the file will use 1 clusters which is 8 sectors, so
 8 X 512 bytes per sector = 4KB – 2KB = 2KB slack space
 NTFS – the file will use 1 cluster which is 4 sectors, so
 4 X 512 bytes per sector = 2KB – 2KB = 0 slack space
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So, what does this all mean to us, as
Windows XP users?
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The bigger your disk – the bigger your clusters
(because there is a maximum number of
clusters per disk).
One way to help alleviate the problem of slack
space is to partition the hard drive into smaller
“drives”. Reducing the drive size will reduce
the cluster size.
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So what can cause problems with a Disk?
Physical hard drive problems:
• Wear and tear on hard disk - Minimize with Power
Management and/or Hibernation
• Head crash - Minimize by placing system where it will not
get knocked around.
Software-related problems:
• Viruses -Minimize by using virus protection software
Some error causing conditions to data that may be
repairable:
 Power surges
 Power outages
 Locked system
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Cleaning Up Your Disk
 Computer performance depends a great
deal on the hard drive.
 Need disk space for:
 New files
 Temporary files
 Documents waiting to be printed
 Cache files
 Cache – storage area for often used information that
can be accessed quickly
 Recycle
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Cleaning Up Your Disk
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Disk cleanup is a utility that helps maintain the hard
disk.
Intended for hard drives.
Will remove the following;
 Internet cache files
 Downloaded program files
 Offline web pages
 Offline lines, & temporary offline files
 Temporary files
 Files in the recycle bin
 Windows components that you no longer use
 Installed programs that you no longer use
 Catalog files for the Content Indexer
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Check Disk
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The Check Disk utility is a disk analysis
and repair utility that examines disks for
errors and, where possible, repairs errors.
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Checks the logical structure
Checks the physical integrity of the disk’s
surface, if it finds a bad sector it will
attempt to move the data to another
location.
Take care of Lost Clusters
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What are lost clusters?
Lost Clusters:
Have no directory entry in directory table
• Do not belong to any file
• Take up disk space • Unavailable for new data
• Cannot be retrieved/deleted
•
• Reasons for Lost Clusters
• Not exiting program properly
• Power surge/failure
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Lost Clusters Example
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Check Disk can fix lost clusters
 Can fix lost clusters automatically
or
 Save them to disk as files
Side note:
You can check if you have lost clusters by clicking
on a file and comparing the file size in explorer
window to status bar files size.
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Check Disk continued
 CAN check/repair local hard drives,
floppy disks, and removable drives
 CANNOT find/fix errors on CD-
ROMs or network drives
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Check Disk, continued
Should be used on a regular basis
 The first time you use it you should back up your disk
before running check disk.
 Close all open programs when using this program,
including screen saver
 If disk is formatted as NTFS, Windows XP Professional
will automatically (without running Check Disk):
Log all file transactions
Replace bad clusters
Store copies of key information for all files on NTFS
volume
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Contiguous and
Noncontiguous Files
Windows XP Professional keeps track of data by
placing it into a file.
To store and retrieve files:
 Disk divided into sectors
 Sectors grouped into clusters
Number of sectors in a cluster is determined by
Size of the hard drive
File allocation system – FAT, FAT32, NTFS, etc.
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Contiguous and
Noncontiguous Files
When a file is deleted:
 Only entries in FAT deleted
 Space file occupied becomes
available
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Contiguous and
Noncontiguous Files
Files are:
 Contiguous – written to adjacent clusters
on a disk
 Noncontiguous (fragmented) – written to a
disk in nonadjacent clusters.
So a Fragmented Disk has noncontiguous files.
It takes longer to read a Fragmented Disk
because the head must move around so
much going to the various locations of the
file clusters.
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Defragmentation
Rearranges the files on a disk so that all
parts of each files are store in consecutive
clusters.
 It also records the clusters for one file right
after the clusters for another file, and in the
process, removes free space between files that
would result in more fragmentation.
 At the end of defragmentation all the unused
space is near the inner edge of the disk.
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Defragmentation, continued
Prior to running Disk Defragmenter:
Run Check Disk and Disk Cleanup
Close All open programs
Allow ample time, can take hours –
depends on how fragmented your disk
is.
Back up disk
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