File Organization and Storage

File Organization & Storage

• A file is a collection of data stored under permanent or non-volatile storage.
• A file is data stored in one unit, identifiable by a filename, such as a document, picture, audio/video, or application.
• Files can be stored on various mediums, including disks, hard drives, tapes, and optical media, retaining information even when powered off.

Basic File Operations

• Opening a file links a logical file to a physical one.
• Closing a file severs the link between physical and logical files.
• Key operations include reading, writing, and seeking a specific source file.
• Detecting the end of a file and I/O errors are file operations.

Good File Organization

• File organization characteristics include quick access, great capacity, reduced disk accesses, and growth management via collections splitting.
• Organizing files ensures related information is quickly accessible.
• Optimizing file organization minimize disk accesses needed to obtain the necessary information

File Organization with Tags

• File organization can be improved by adding tags
• This is found in properties -> details

File Types

• Common audio file types: .MP3, .M4A, .AAC, .WMA, .OGG, .WAV, .PCM, .FLAC
• Common video file types: .MP4, .MOV, .AVI, .MPG, .WMV, .MKV, .FLV, .MTS
• Common image file types: .JPG, .PNG, .TIF, .GIF, .BMP, .PSD
• Common document file types: .DOCX, .PPTX, .XLSX, .PDF, .TXT, .RTF, .CSV
• Other file types: .ZIP, .RAR, .DMG, .EXE, .HTML, .PHP

Computer File Classification

• Physical files physically exist on secondary storage, are known by the OS, and appear in the file directory.
• Logical files act as a channel hiding location and format details from the program.

File Properties

• Files exist as clusters on a disk, each cluster being 512 bytes.

Elements of a Computer File

• Records are collections of related fields that represent single entities, such as student records with admission number, name, and marks.
• Fields are single characters or a collection of characters representing a single piece of data, e.g., a student's admission number.
• Characters are the smallest element in a computer file, consisting of letters, numbers, or symbols made of seven or eight bits.

File Compression

• Compressed files archive reduced-size files.
• Example shown of converting "AAABBBBBCC" to "3A5B2C"
• Compression sample:
  • "Ask not what your country can do for you -- ask what you can do for your country" contains 79 units uncompressed
  • The above when compressed is "1 not 2 3 4 5 6 7 8 -- 1 2 8 5 6 7 3 4" containing 40 units
  • Further compression yields "1not__2345__--__12354" with 18 units

Common File Types for Compression

• Common compression file types: 7z, Alz, Arc, Cab, Car, Cfs, Dar, Dm, Egg, Ice, Jar, Pak, Rar, Sqx, Zip

Compression Experiment

• Compressing an already compressed file will result in a limited reduction in size, not zero.
• Files can be compressed on phone

Types of Storage

• Common storage types include Hard Disks, Solid-State Drives, USB Flash Drives, Memory Cards, and Optical Discs
• Other storage types: magnetic stripe cards, smart cards and RFID Tags

Magnetic Stripe Cards

• Magnetic stripe cards contain information via a magnetic stripe.

Smart Cards

• Smart cards store data on an integrated circuit.

RFID Tags

• RFID tags consist of an antenna and memory chip that transmits data via radio waves.
• An RFID reader reads the signal and transfers it to a computer.

RFID Applications

• RFID is used in inventory management, access control, animal tracking, personnel tracking, and asset tracking

NFC-Enabled Devices

• NFC-enabled devices contain an NFC chip and the antenna transmits information

Network Attached Storage (NAS)

• Network attached storage is a server on a network providing storage to users
• Network Attached Storage (NAS) facilitates shared storage for network-connected devices.

Cloud Storage

• Cloud storage provides services like dropbox, google drive, apple icloud, Ms One Drive and BaiduYun.
• Benefits of cloud storage: accessibility anywhere, easy sharing, backup.
• Downsides of cloud storage include internet reliance, cost, and online security exposure.

Enterprise Storage

• Enterprise hardware offer large organizations access to managing and storing data and information
• Redundant Array of Independent Disks (RAID) is implimented in enterprise storage

RAID Technology

• RAID (Redundant Array of Independent Disks) is a technology for placing data across multiple disks.
• RAID facilitates input/output (I/O) overlap to improve performance.
• RAID can use hardware (RAID controller) or software (Virtualization)

RAID 0

• Data in RAID 0 is split into blocks and written across multiple drives
• Requires the use of 2 disks at the same time

RAID 0 Advantages

• Yields superior I/O performance and utilizes all storage capacity
• There is no overhead caused by parity control

RAID 0 Disadvantages

• If one drive fails, this results in data loss

RAID 0 Ideal Use

• Raid 0 is ideal for non-critical storage of data
• Ideal for something that is read and written at a high speed

RAID 1

• Data is stored twice and written to a data drive and a mirror data drive
• Requires at least 2 drives

RAID 1 Advantages

• Data isn't lost in case of drive failure

RAID 1 Disadvantages

• Half of storage capacity is lost because all data is written twice

RAID 1 Ideal Use

• Ideal for mission critical data like accounting systems

RAID 5

• Employs block-level stiping with parity
• Parity information is striped across each drive so it functions if one drive fails

RAID 5 Advantages

• Even when a drive fails users still have access to all the data even while it is being replaced

RAID 5 Disadvantages

• Restoring data can take a day or more so the rebuild time is slower
• Data is lost forever if another disk fails during the rebuild time

RAID 5 Ideal Use

• Ideal for file and application servers

RAID 1+0 (10)

• Combines RAID 1 and RAID 0 so data is mirrored and the mirrors are striped

RAID 1+0 (10) Advantages

• If something goes wrong it can be rebuilt quickly

RAID 1+0 (10) Disadvantages

• Half of the storage capacity is lost because of mirroring so it is expensive

RAID 1+0 (10) Ideal Use

• Ideal for servers that have highly utilized databases and that perform heavy write operations

Summary

• Definition of a file and its operations
• Good file structure characteristics
• Elements of a computer file
• Type of computer files
• Types of file storages