The document discusses different types of storage mediums and file systems, and how fragmentation can occur. It explains that file systems use allocation methods to manage how file data is stored in blocks across storage devices. Common allocation methods include contiguous, non-contiguous, and indexed allocation. Fragmentation happens when file blocks are not stored contiguously, slowing access. Defragmentation reorganizes blocks to improve performance.

1. Running head: STORAGE MEDIUMS AND FRAGMENTATION 1
Storage Mediums and Fragmentation
Larry Reid
Kaplan University
IT332-01 Principles of Information Systems Architecture

2. STORAGE MEDIUMS AND FRAGMENTATION 2
Storage Mediums and Fragmentation
There are several types of storage mediums and each of those mediums needs a file
system to be useful. A lot of file systems suffer from the effects of fragmentation and some
storage mediums become slow overtime needing to be defragmented. Sometimes it’s difficult to
wrap our heads around concepts like this but this article is meant to make it as painless as
possible to grasp these concepts and come to an understanding.
what are file system allocation methods?
A file system is what is used on a storage device to manage, maintain, and organize all of
the data on it. File systems are things such as the New Technology File System (NTFS) used by
Windows which stores data contiguously and uses indexing allocation, the File Allocation Table
32 (FAT32) and extended FAT (exFAT) which both use the File Allocation Table with linking,
the Hierarchical File System Plus (HFS+) used by Apple which is extent-based allocation with
indexing, and the Linear Tape File System (LTFS) developed by IBM for tape drives which also
has extent-based allocation with indexing. Are you wondering what file system allocation
methods are still? Well they are what explain how blocks are divided up and distributed each
time a file is saved, each allocation method has a different way of defining how addresses to
blocks are stored, some file systems only use one type of allocation method and others take the
best from multiple methods and put them together. File systems are rules or a blueprint that the
operating system follows in order to write, read, organize, and manage files all of which use
some type of table with addresses to sectors and blocks, some keep track of how many blocks the
file takes up, and others may be links to a block and then to another until they get to one that
doesn’t have a link, which means the whole file has been found.
Now let’s go over the different types of allocation. Contiguous allocation is method used
to store data in a sequential set of blocks. When you save a file using this allocation method,

3. STORAGE MEDIUMS AND FRAGMENTATION 3
your file system has to figure out how many blocks are needed to store the file, and it then has to
find free space on the disk with the amount of blocks needed, if it can’t find the space needed
then it will fragment the file and place it in two or more sets of contiguous blocks. Using this
method is the fastest way to access files for Hard Disk Drives (HDD) since the head does not
have to move all over the disk to find all of the blocks that a file is stored on (Evett, 2015).
Non-Contiguous allocation doesn’t care about allocating sequential blocks, they can be
all over the disk and the files will have links to the next block that comprises more of the file
until the last block which doesn’t contain a link, is reached, or it may store the file block
locations in a master list. Non-Contiguous allocation does not have external fragmentation but
does contain internal fragmentation (Englander, 2014).
Indexed allocation uses index tables to store all the block addresses for each file. Each
file gets its own index table typically stored in the first block allocated to the file. Additionally,
there is a file management system that is used to maintain a directory that houses information
about the files that can include attributes, the link locations, the pointer to the file, file name, etc.
Whey a file is opened the operating system will store the files index table, that houses the links
to all of the files blocks, in memory making it extremely fast to do random accesses to the file
and also very efficient with memory usage. Typically, this is a non-contiguous allocation method
but Windows NTFS allocates contiguous blocks as much as possible to save additional memory
(Englander, 2014).
Tape allocation is simpler than disk allocation. This is meant more for sequential reads
and not really feasible for random access. Tape drives can be compacted, similar to
defragmented, but it’s usually not worth the work, it would be easier to copy the data to another
tape. The Linear Tape File System is a great method to use for storing files on a tape drive, using
extent-based allocation along with indexing it allows the tape to almost act like a hard drive,

4. STORAGE MEDIUMS AND FRAGMENTATION 4
allowing for random read access. Though if the files need to be accessed more often, it would be
more efficient to move or copy the files to a disk drive. Tape drives are better to be used for
daily, weekly, or monthly backups (Englander, 2014).
Disk allocation and storage allocation has to do with how a disk is broken up into zones,
sectors, and blocks. So disks contain zones which are the tracks that contain the same number of
blocks as adjacent tracks, so as you move closer to the center of the disk the zones change. Next
we have sectors which are a section, shaped like a pie slice, that contain blocks, and blocks are 4
or 5 kilobyte sections on the disk. There are also OS blocks that are described by the operating
system, one block for the OS can contain multiple disk blocks. What happens in disk allocation
is the contiguous, non-contiguous, or whatever allocation method you are using, will allocate
these blocks to the free disk space manager on the operating system and the OS will use the free
disk space manager to allocate the disk blocks for storage (Dittrich, 2013).
Partitions are divisions created within a disk, you can have between one and three
primary partitions and one additional extended partition on a single simple disk volume. An
extended partition can have several logical partitions created within it, which is how we can get
around the four partition rule on hard disks. Additionally, we can create a dynamic disk which
allows us to create several logical volumes which are generally the same as a partition but
instead of the space residing on a single disk the logical volume can span across multiple disks.
A physical volume refers to a physical hard disk in its entirety (Indika, 2011).
Fragmentation can be broken up into two types, internal and external. Internal
fragmentation is the space reserved by the file system to store index tables, FAT tables, and any
other unused space that is set aside within a file, such as the reserved space for file expansion.
External fragmentation refers to how a file is saved to the disk blocks. If a file must be broken up
across the disk to be saved and is not saved in a contiguous manner, then it is considered

5. STORAGE MEDIUMS AND FRAGMENTATION 5
fragmented and the disk heads have to move, possibly, several times to write or read the file
creating slower file read/write times. Defragmentation takes all of the broken up non-contiguous
files and puts them in as much of a contiguous order as it can and then compresses all of the files
together to fill in all of the little blocks of free space between files, which were created from
deleting files. Defragmentation is used to make it easier for the disk heads to find files, and
speeds up read/write operations that were slow because of fragmentation.
The table below displays several different storage mediums, file systems, allocation
methods, and various attributes about each of them.
NTSF FAT32 exFAT HFS+ LTFS
Can Produce
Fragmentation
Issues/Problems
Contiguous
Allocation
No No No No No Yes
Fragmentation, finding space for files,
knowing file size, needs to compress files
Linked
Allocation
No No No No No No
Files can be scattered everywhere, uses links
stored with each block and if one block loses
its link the whole file is lost, not efficient
Indexed
Allocation
Yes -with contiguous
block allocation
No No No No Yes
Internal fragmentation is bad because of
allocating index tables for each file, Index
tables can create wasted space
File Allocation
Table (FAT)
No
Yes -Uses links at each
file but has all links
stored in fat table
Yes -with contiguous
block allocation
No No No
Not really recommended for running full
operating systems on, better for embeded
systems, small devices, and removable storage
Extent-Based
Allocation
No No No Yes -with indexing Yes -with indexing Yes
Suffers from both internal and external
fragmentation
Has Journaling
Feature
Yes No No
No - but it can be turned
on through the
command line
No N/A N/A
Max Volume
Size
16TB 2TB
64ZB - Recommended
Max is 512TB
8EB 2.5TB N/A N/A
Max Single File
Size Read/Write
16TB 4GB 64ZB 8EB 2.5TB N/A N/A
Allocation Unit
Sizes
4096b - 64KB 512b - 4KB 16KB - 32MB 4096b - 64KB 16KB - 256KB N/A N/A
Can Produce
Fragmentation
Yes -but its decreased
with larger allocation
unit sizes when
formatting
No
Yes -but fragmentation
does not cause as many
issues unless your using
an HDD.
Yes
Yes -internal
fragmentation only, LTFS
cannot be defragmented,
unless it is reformated
N/A N/A
Flash Drive Yes Yes Yes Yes No
Yes -very little effect on
solid state storage
Low maximum write cycles,
HDD Yes Yes Yes Yes No
Yes -slows file
read/write speed over
time, needs to be
defragmented
Uses physical heads and spinning disk,
fragmentation can slow performance a lot
SSD Yes Yes Yes Yes No
Yes -very little effect on
solid state storage
SSD's offer very fast access but have a
relatively short lifespan and are very expensive
SD Card Yes Yes Yes Yes No
Yes -very little effect on
solid state storage
Limited on write cycles, slow read/write speeds
Tape Drive No No No No
Yes -lets users navigate
and interact like its a
hard disk drive
No
Cannot be accesed randomly, though they can
be very fast and easy to use for backups
Windows
Compatible
Yes
Yes -but optomize for
quich removal option
needs to be turned off to
format FAT32 drives
Yes Read Only
Yes
need special software
and hardware
N/A N/A
Mac
Compatable
Read Only Yes Yes Yes
Yes
need special software
and hardware
N/A N/A

6. STORAGE MEDIUMS AND FRAGMENTATION 6
References
Englander, Irv. (2014-01-21). The Architecture of Computer Hardware and System Software: An
Information Technology Approach, 5th Edition. [VitalSource Bookshelf Online].
Retrieved from https://kaplan.vitalsource.com/#/books/9781118803127/
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Microsoft, (2016). Description of the exFAT file system driver update package. retrieved May 23
2016, from Microsoft Web Site: https://support.microsoft.com/en-us/kb/955704
LeGault, L (2009). HFS+: The Mac OS X File System. retrieved May 23 2016, from Dep. of
Computer Science University of Wisconsin-Madison Web Site:
http://pages.cs.wisc.edu/~legault/miniproj-736.pdf
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Web Site: http://searchdatabackup.techtarget.com/definition/LTFS-Linear-Tape-File-
System
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from IBM Web Site: http://www-
01.ibm.com/support/docview.wss?uid=ssg1S7003166&aid=3
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