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1409 Operating Systems and Shell Scripting > Week 7 > Flashcards

Week 7 Flashcards

1
Q

What are HDDs?

A

Hard Disk Drives (HDDs) spin platters of magnetically-coated material under moving read-write heads. The drives rotate 60 to 250 times per second.

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2
Q

What is transfer rate?

A

Transfer rate is the rate at which data flow between drive and computer

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3
Q

What is positioning time?

A

Positioning time (random access time) is the time to move a disk arm to desired cylinder (seek time) and time for desired sector to rotate under the disk head (rotational latency)

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4
Q

What is a head crash?

A

A head crash is where a disk head makes contact with the disk surface and this is bad

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5
Q

What are some non-volatile memory devices?

A
  1. Hard Disk Drives
  2. Solid State Disks
  3. USB drives
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6
Q

What are two types of volatile memory?

A
  1. DRAM (Direct Random Access Memory)
  2. RAM (With many names, including RAM disks)
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7
Q

What are magnetic tapes?

A

Magnetic tapes are an early secondary storage medium. They are non-volatile and can hold large quantities of data but have slow access time.

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8
Q

How does address mapping work with disk drives?

A

Disk drives are addressed as large 1-dimensional arrays of logical blocks, where the logical block is the smallest unit of transfer. The 1-dimensional array of logical blocks is mapped into the sectors of the disk sequentially.

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9
Q

What is disk bandwidth?

A

Disk bandwidth is the total number of bytes transferred, divided by the total time between the first request for service and the completion of the last transfer.

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10
Q

What are some sources of disk I/O requests?

A
  • Operating system
  • System processes
  • Users processes
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11
Q

What do I/O requests include?

A

I/O requests include input or output mode, disk address, memory address, number of sectors to sectors to transfer

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12
Q

What are the three types of HDD scheduling algorithms?

A
  1. First Come First Serve (FCFS) - The requests are worked on from start to finish
  2. SCAN - The disk arm starts at one end of the disk and services requests while moving towards the other end and then is reversed when it reaches the other side
  3. C-SCAN - The disk arm starts at one end of the disk and services requests while moving towards the other end however when it reaches the other side of the disk it returns to the start of the disk without servicing any requests on the way
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13
Q

What does error detection do?

A

Error detections determines if a problem has occurred. If a problem is detected the operation can be halted. Error detection is frequently performed via parity bit, where each byte in a memory system has a parity bit. If the number is even the parity is set to 0 if the parity is odd the number is set to 1.

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14
Q

What is ECC?

A

Error correction code (ECC) detects errors and can correct soft errors but cannot correct hard errors.

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15
Q

What is low-level formatting?

A

Low-level formatting or physical formatting is the process of a dividing a disk into sectors that the disk controller can read and write.

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16
Q

What is bootstrap?

A

Bootstrap is the initial program that is ran when the computer is first powered up. The bootstrap is mostly stored in NVM flash memory

17
Q

What is the boot partition?

A

The boot partition contains the OS and device driver

18
Q

What is swap space management?

A

Swap space management is a technique used for moving entire processes (swapping), or pages (paging), from DRAM to secondary storage when DRAM not large enough for all processes. This technique is provided by the operating system.

19
Q

What are the three ways that computers access storage?

A
  1. Host-attached - access through local I/O ports (USB, Thunderbolt)
  2. Network attached - storage made available over a network rather than over a local connection
  3. Cloud - provides access to storage across a network, unlike NAS, accessed over the Internet or a WAN to remote data centre
20
Q

What is RAID?

A

Redundant array of inexpensive disks (RAID) is a disk organisation technique where multiple disk drives provide reliability via redundancy.

21
Q

What is mirroring?

A

Mirroring is the technique of duplicating every drive to increase redundancy. This is the simplest but most expensive technique

22
Q

What is striping?

A

Striping is where a group of disks is used as one storage unit and this can improve transfer rate.

23
Q

What is RAID level 0?

A

RAID level 0 refers to drive arrays with striping at the level of blocks but without any redundancy

24
Q

What is RAID level 1?

A

RAID level 1 refers to drive mirroring

25
Q

What is RAID level 0 + 1?

A

RAID level 0 + 1 refers to a combination of RAID levels 0 and 1. RAID 0 provides the performance, while RAID 1provides the reliability.

26
Q

What is RAID level 1 + 0?

A

RAID level 1 + 0 drives are mirrored in pairs and then the resulting mirrored pairs are striped.

1409 Operating Systems and Shell Scripting (9 decks)

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