CHAPTER 3: STORAGE
Study Summary • Self-Check Test • Questions to Ask Your Lecturer
Based on the uploaded lecture slides: Understanding Computers: Today and Tomorrow, Chapter 3
1. Storage System Characteristics
• Storage system: consists of a storage medium and a storage device.
• Storage medium: the hardware where data is stored, such as a DVD disc or flash memory card.
• Storage device: the hardware into which the storage medium is inserted, such as a DVD drive or flash memory
card reader.
• Storage can be internal, external, or remote. Most storage media are nonvolatile, meaning they are used to save
data for later use.
• Random/direct access: data can be retrieved from any location on the storage medium.
• Sequential access: data must be retrieved in the order in which it was physically stored; magnetic tape is an
example.
• Storage technologies: magnetic (HDD), optical (optical discs), and electronic/electron-based (flash memory).
2. Hard Drives
• A hard drive stores most programs and data for a personal computer and can be internal or external.
• Magnetic HDD: contains metal disks whose magnetized particles represent data as 0s and 1s.
• Tracks: concentric paths where data is recorded.
• Sectors: small pieces of a track.
• Clusters: one or more sectors.
• Cylinders: a collection of tracks at the same location on a set of hard-disk surfaces.
• Recording technologies: longitudinal magnetic recording, perpendicular magnetic recording (PMR), shingled
magnetic recording (SMR), and heat-assisted magnetic recording (HAMR).
3. SSDs and SSHDs
• SSD: uses flash memory technology, has no moving parts, uses less power, and is much faster than magnetic hard
drives, but is more expensive.
• SSHD: combines magnetic disks and flash memory. Performance-related data is stored in flash memory. It is nearly
as fast as an SSD and slightly more expensive than a magnetic HDD.
4. Internal and External Drives
• Internal drives: permanent storage devices located inside the system unit.
• External drives: used for transporting large amounts of data, backup, and additional storage. Most connect using
USB. Full-sized external drives are often used for backup; portable drives are smaller and easier to transport.
5. Hard Drive Speed, Caching and Partitioning
• Disk access time: total time needed to read or write data; it consists of seek time, rotational delay, and data
movement time.
• SSDs do not require seek time or rotational delays.
• Disk cache: memory used with a magnetic hard drive to improve performance.
• Partitioning: divides the physical capacity of one drive logically into separate areas called partitions. Each partition
functions as an independent logical drive.
• Partitions can be used for recovery, data storage, or a dual-boot system.
6. File Systems and Interface Standards
• File system: determines partition size, cluster size, maximum drive size, and maximum file size. Examples in the
slides include FAT, FAT32, and NTFS.
• Interface standards: determine how a drive connects to a computer. Examples include SATA, SAS, Fibre Channel,
and iSCSI.
7. Optical Discs
• Optical discs are thin circular plastic discs read from and written to using laser beams.
• They use a single spiral track and are commonly used for software delivery, backup, and storing or transporting
music, photos, and video.
• Pits and lands: represent data. A transition between a pit and a land represents 1; no transition represents 0.
• Burning: recording data onto an optical disc using appropriate burning software.
8. Optical Disc Capacities and Types
• CD: normally 700 MB.
• DVD: 4.7 GB single-layer or 8.5 GB dual-layer.
• Blu-ray (BD): 25 GB single-layer or 50 GB dual-layer.
• BDXL: up to 128 GB according to the slides.
• Ultra HD Blu-ray: up to 100 GB and designed for Ultra HD/4K movies.
• Read-only: CD-ROM, DVD-ROM, BD-ROM; cannot be erased and reused.
• Recordable: CD-R, DVD-R, DVD+R, BD-R; can be written to but cannot be erased and reused.
• Rewritable: CD-RW, DVD-RW, DVD+RW, BD-RE; can be written, erased, and overwritten.
9. Flash Memory
• Flash memory is a chip-based storage medium that represents data using electrons.
• It is used in smartphones, tablets, smartwatches and other portable devices and is usually the primary storage for
mobile devices.
• Flash memory cards: contain flash memory chips, a controller chip, and metal contacts. SD is one of the most
widely used types.
• USB flash drives: integrate flash memory into a small self-contained unit powered through a USB port and are
designed to be portable.
10. Network, Cloud and Smart-Card Storage
• Remote storage: storage that is not connected directly to the user's computer.
• NAS: Network Attached Storage; high-performance storage connected individually to a network.
• SAN: Storage Area Network; a separate network of hard drives or other storage devices attached to the main
network.
• Cloud storage: storage accessed through the Internet. It can be used for backup and synchronization, and many
services offer some free storage.
• Smart card: credit-card-sized plastic containing computer circuitry, including processor, memory and storage. It
stores a small amount of data and can contain personal or biometric information.
11. Large Storage Systems
• Storage servers contain multiple high-speed hard drives, are larger than typical NAS systems, and can be expanded
by adding more drives.
• They can use Fibre Channel or iSCSI connections and can contain magnetic drives, SSDs, or both.
12. RAID
• RAID: Redundant Arrays of Independent Disks. It is a method of storing data on two or more drives that work
together.
• Purpose: protect critical data and increase fault tolerance.
• RAID 0: disk striping — spreads files/data over two or more hard drives.
• RAID 1: disk mirroring — creates a duplicate copy.
• Other RAID levels can combine striping and mirroring.
13. Archival Storage
• Data archiving: identifying and moving data that is no longer actively used from regular storage to a separate
long-term archival system.
• Options in the slides include large hard drives, magnetic tape, archival Blu-ray discs, optical jukeboxes, and cloud
storage.
14. Evaluating Storage Alternatives
• When choosing storage, consider speed, compatibility, storage capacity, convenience, and portability.
• Storage alternatives involve trade-offs, so the appropriate solution depends on the device and the intended use.
SELF-CHECK TEST
Try to answer without looking at the summary. Answers are included at the end.
Part A — Multiple Choice
1. What is the hardware where data is actually stored called?
A. Storage device
B. Storage medium
C. Processor
D. Interface
2. Which type of access retrieves data directly from any location?
A. Sequential access
B. Random access
C. Linear access
D. Serial access
3. Which technology does a traditional HDD use?
A. Optical
B. Magnetic
C. Electronic
D. Laser
4. Which drive has no moving parts?
A. HDD
B. SSD
C. Magnetic tape
D. Optical drive
5. Which HDD technology overlaps tracks like roof shingles?
A. PMR
B. HAMR
C. SMR
D. SATA
6. What is the standard capacity of a single-layer DVD?
A. 700 MB
B. 4.7 GB
C. 25 GB
D. 50 GB
7. Which optical disc can be erased and rewritten?
A. CD-ROM
B. DVD-R
C. BD-R
D. DVD-RW
8. What is the most common type of flash memory card mentioned in the slides?
A. SD
B. CD
C. DVD
D. HDD
9. Which storage technology is accessed through the Internet?
A. RAID
B. Cloud storage
C. Internal storage
D. Optical storage
10. RAID 1 is known as:
A. Striping
B. Mirroring
C. Partitioning
D. Caching
Part B — True or False
11. Storage media are generally nonvolatile. True / False
12. SSDs use spinning magnetic disks. True / False
13. A sector is a small piece of a track. True / False
14. DVD-RW discs can be erased and rewritten. True / False
15. Cloud storage can be used for backup. True / False
16. RAID 0 uses disk striping. True / False
17. RAID 1 uses disk mirroring. True / False
18. Magnetic tape is an example of sequential storage. True / False
19. Flash memory is commonly used in smartphones. True / False
20. Partitioning divides one physical drive into logical areas. True / False
Part C — Short Answer
21. Explain the difference between a storage medium and a storage device.
22. Explain the difference between random access and sequential access.
23. Give three differences between an HDD and an SSD.
24. What are tracks, sectors, clusters, and cylinders?
25. What is disk partitioning?
26. Explain the difference between CD-ROM, CD-R, and CD-RW.
27. What are pits and lands?
28. What is flash memory?
29. Explain the difference between NAS and SAN.
30. What is RAID and why is it used?
QUESTIONS TO ASK YOUR LECTURER
These questions focus on understanding the chapter and connecting it to cybersecurity and digital
forensics.
Storage fundamentals
• Why is storage considered nonvolatile while RAM is volatile?
• What is the practical difference between logical and physical file representation?
• What determines whether a storage system uses random or sequential access?
HDD, SSD and partitions
• Why are SSDs faster than HDDs if both store the same types of files?
• What are the main reasons someone might still choose an HDD instead of an SSD?
• How does disk caching improve HDD performance?
• How does partitioning affect the organization and management of data?
Digital forensics connection
• How does the difference between HDD and SSD affect digital forensic investigations?
• What happens to deleted data on an SSD compared with an HDD?
• How can disk partitions affect forensic evidence acquisition?
• Why is it important for a forensic investigator to understand the physical and logical representation of files?
• How can encryption on a storage device affect a forensic investigation?
• What storage characteristics should a forensic investigator document before acquiring evidence?
RAID and cloud
• If RAID protects against drive failure, does RAID replace the need for backups? Why?
• What forensic challenges can arise when investigating cloud storage?
• How would evidence acquisition from NAS differ from evidence acquisition from a normal computer?
• What happens to evidence when data is distributed across multiple RAID drives?
Exam-focused
• Which storage concepts from this chapter are most likely to appear in the exam?
• Should we be able to compare HDD, SSD, SSHD, optical, flash and cloud storage in an exam?
• Do we need to know the differences between RAID levels beyond RAID 0 and RAID 1?
• Will we be expected to calculate storage capacities involving MB, GB and TB?
• Which diagrams from this chapter should we be able to draw and explain?
ANSWER KEY
1. B
2. B
3. B
4. B
5. C
6. B
7. D
8. A
9. B
10. B
11. True
12. False
13. True
14. True
15. True
16. True
17. True
18. True
19. True
20. True
Short-answer marking guide
• 21. Medium = where data is stored; device = hardware used to access the medium.
• 22. Random/direct access can retrieve data from any location; sequential access retrieves data in stored order.
• 23. HDD uses magnetic disks and moving parts; SSD uses flash memory and no moving parts; SSD is faster and
uses less power but is more expensive.
• 24. Tracks are concentric recording paths; sectors are pieces of tracks; clusters contain one or more sectors;
cylinders are corresponding tracks across disk surfaces.
• 25. Dividing one physical drive logically into separate partitions.
• 26. ROM is read-only; R is recordable but not erasable/reusable; RW is rewritable.
• 27. Physical features used on optical discs to represent data; transitions represent 1 and no transition represents 0.
• 28. Chip-based storage that represents data using electrons.
• 29. NAS is storage connected individually to a network; SAN is a separate network of storage devices attached to
the main network.
• 30. RAID uses multiple drives working together, helping protect critical data and increase fault tolerance.
Priority revision list: Storage medium vs device; random vs sequential access; HDD structure; HDD vs SSD;
partitions; optical disc types; flash memory; NAS/SAN/cloud; RAID 0 vs RAID 1; archival storage; storage evaluation
criteria.