Podcast
Questions and Answers
What is the primary role of the file allocation table (FAT) in disk storage?
What is the primary role of the file allocation table (FAT) in disk storage?
In a stack of platters, how many sides are typically used for positioning information?
In a stack of platters, how many sides are typically used for positioning information?
Which of the following allows NAND cells to be preferred over NOR cells in storage applications?
Which of the following allows NAND cells to be preferred over NOR cells in storage applications?
What is the starting track number where storage begins on a disk?
What is the starting track number where storage begins on a disk?
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What condition may lead to file fragmentation on a disk?
What condition may lead to file fragmentation on a disk?
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What is the primary reason NAND cells are favored over NOR cells in terms of space efficiency?
What is the primary reason NAND cells are favored over NOR cells in terms of space efficiency?
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How does the structure of a stack of platters contribute to data storage?
How does the structure of a stack of platters contribute to data storage?
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In the context of disk storage, what arrangement defines the boundaries of data allocation?
In the context of disk storage, what arrangement defines the boundaries of data allocation?
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Why might files stored on a disk experience fragmentation?
Why might files stored on a disk experience fragmentation?
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What characteristic of tracks on a disk defines their functionality?
What characteristic of tracks on a disk defines their functionality?
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Study Notes
Types of Computer Storage
- Volatile memory loses data when power is off.
- Non-volatile memory retains data when power is off.
- CPU is a fast non-volatile memory with less storage capacity.
- Cache is a primary storage memory that is faster than non-volatile memory.
- RAM is primary storage that has a larger storage capacity than volatile memory.
- Data in RAM can be easily transferred, while data in non-volatile memory is not.
- RAM is more costly per unit size compared to non-volatile memory.
- The CPU directly accesses RAM data, but not non-volatile data.
- Processes in RAM can read and write data.
- Data in non-volatile memory can only be read.
- Volatile memory affects system performance significantly.
- Examples of volatile memory: RAM and cache memory
- Examples of non-volatile memory: ROM and hard disk drives (HDD)
Evolution of Data Storage
- 8-inch floppy disks were commercially available in 1971.
- 5 1/2-inch floppy disk were commercially available in 1976.
- USB drives were commercially available in 2000.
- SD cards were commercially available in 2010.
- MicroSD cards were commercially available in 2010.
- Cloud storage became available around 2009.
- Maximum capacity of 8-inch floppy disks is 1.2 MB.
- Maximum capacity of 5 1/2-inch floppy disks is 1.2 MB.
- Maximum capacity of USB drives is 2 terabytes (TB).
- Maximum capacity of SD cards is 256 GB.
- Maximum capacity of MicroSD cards is 128 GB.
- Estimated maximum capacity of cloud storage is 5 Zettabytes (ZB)
- Cost per gigabyte (GB) for 8-inch floppy disks was £1000.
- Cost per GB for 5 1/2-inch floppy disks was £800.
- Cost per GB for USB drives was £0.5.
- Cost per GB for SD cards was £0.8.
- Cost per GB for MicroSD cards was £0.5.
- Estimated free storage space for cloud storage is less than 50 GB.
Hard Disk Drive (HDD) and Solid State Drive (SSD)
- HDDs use platters with read/write heads.
- SSDs use NAND flash memory and a controller.
- HDDs are shock-resistant up to 350g/2ms, and SSDs are up to 1500g/0.5ms.
- Data on HDD is stored in tracks and sectors.
Hard Disk Drive Structure
- Tracks are circular paths on a disk.
- Sectors are divisions of tracks.
- Clusters are groups of sectors storing data.
- A stack of 2 or more platters has 3 sides for data and 1 for positioning.
- Data is stored in tracks, divided into sectors.
- The FAT (File Allocation Table) program uses sectors to save data.
- Tracks start at 0 and move outward to 1023.
- Files can fragment when a disk is full.
Hard Drive Read/Write Head
- Reads and writes data using electromagnetic fields.
- The head has read and write parts in a T shape.
- Data is stored as magnetic fields.
Solid State Drive (SSD)
- SSDs have a host interface logic.
- SSDs use flash memory packages and a controller for processing data.
- SSDs have a processor and a buffer manager.
- SSDs have a specific architecture for storage and retrieval of data.
- SSDs use a buffer to store data fetched by the CPU.
SSD Storage Mechanism
- Fowler-Nordheim tunneling.
- Channel hot electron injection.
SSD vs. HDD
- SSD access times are typically 0.1 ms, HDDs are 5.5-8.0 ms.
- SSDs deliver at least 6000 I/O's per second. HDDs deliver up to 400.
- The failure rate of SSDs is less than 0.5%. The rate of HDDs fluctuates between 2-5%.
- SSDs consume between 2 and 5 watts of power. HDDs use 6-15 watts.
- Average I/O wait for SSDs is 1%. For HDDs, it is about 7%.
- Average service time for SSDs with a backup is under 20ms, and HDDs is 400-500ms.
- SSD backups take about 6 hours. HDD backups take 20-24 hours.
USB
- USB connectors exist in different types (e.g., A type, B type, Micro-B, Type-C).
- USB data transfer rates vary (e.g., 12 Mbps, 480 Mbps, 4.8 Gbps).
- USB standards have evolved with increased speeds over time.
Alternative Storage Options
- CDs and DVDs use laser beams to read and write data.
- Tapes use magnetic fields to store data on a moving magnetic medium.
DNA Storage
- Data can be stored as DNA sequences.
- Errors can arise in reading data from DNA.
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Description
Explore the differences between volatile and non-volatile memory, including RAM, cache, and their impact on system performance. Dive into the history of data storage evolution from floppy disks to modern storage solutions.
