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COSC 118 > Lecture 10 > Flashcards

Lecture 10 Flashcards

1
Q

Operating System Definition:

A
  • Provides an interface for users and applications to access the computer’s hardware.
  • Controls access to memory, CPU, HDD/SDD and other peripheral devices connected to the PC.
  • Consists of File system, User Interface, and Kernel
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2
Q

Operating System Layers

A
  1. User applications
  2. User mode
    - Services
    - Application interfaces
  3. Windows Kernel
    - Task scheduler
    - Memory manager
    - File system manager
    - GUI manager
    - Hardware Abstraction Layer (HAL)
  4. Hardware
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3
Q

File System Definition:

A
  • Used for storing and managing files stored on the PC or on the network to which it is connected.
  • Storage organization using hierarchical filing method using folders and files
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4
Q

Hierarchical Filing Syntax and Definition:

A
  • Folders/subfolder(s)/subfolder(s)/file(s)
  • Can be accessed through GUI or CLI (terminal)
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5
Q

File Index System:

A
  • The OS maintains a database of files and locations
  • This db is updated as files are created, modified or deleted.
  • Helps users search for files by simply knowing a part of the name only or type.
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6
Q

User Interface:

A
  • An interface for interacting with the contents in storage.
  • Can be Graphical (GUI) or text-based (CLI / terminal)
  • Associates file types with applications or actions,
    For instance, with GUIs you double click a document to open
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7
Q

Kernel

A
  • Schedules processes and tasks onto the CPU, taking priorities into consideration.
  • Manages memory allocation, ensuring that two apps. do not simultaneously try to assess the same memory space.
  • Interfaces with the hardware
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8
Q

Client vs Server OS:

A
  • Mostly the same, except that server OS can handle more service requests and of varied types.

The server OS can also run client applications, such as MS Excel.

Servers also can also run client variants of certain services, such as DHCP client – because like clients, they also can be configured to use dynamic IP addresses.

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9
Q

Client vs Server OS example:

A

Example: Active directory, DHCP, DNS, RADIUS etc.

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10
Q

Server OS use cases

A

AAA - User authentication, authorization and accountability
(radius server, TACAS+)

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11
Q

Managing user accounts & policies in a domain: Active Directory Server / Access control

A
  • For access control and policy management. (no web browsing during work hours, or no flash drives enabled/allowed)
  • Access to printer or R/W/F access on files
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12
Q

Active Directory Server / Access control is windows based and runs on:

Linux equivalent runs on:

A

LDAP

Lightweight Directory Access Protocol

Network Information System (NIS)

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13
Q

NAS acronym:

A

Network attached storage

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14
Q

NAS definition:

A
  • A dedicated server device designed for providing shared storage for network users.
  • Can also be A regular Windows server hardware running a NAS software
  • it is a SINGLE device
  • Usually connected to the network via Ethernet
  • Can be integrated with Windows AD for AAA
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15
Q

NAS consists of a bunch of disks which appear to users as network mounted volumes. The disks can be configured using different types of ___.

A

RAID config.

  • Can be integrated with Windows AD for AAA
  • Relatively inexpensive and easy to setup
  • Usually connected to the network via Ethernet
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16
Q

Raid definiton

A

Redundant Array of Independent Drives or Redundant
Array of Inexpensive Disks

17
Q

RAID 0:

A

Striping:

  • Combines all the disks together with all
    appear as one entity to users.
  • Easy to setup and makes FULL use of all the disk space.
18
Q

RAID 1

A

Mirroring:

the set of disks are split into 2 halves with each
mirroring the other

Better redundancy but scarifies half the total storage size

19
Q

RAID 5

A

Striping + Parity:

  • Requires minimum of 3 disks.
  • Data is striped across the disks, but the
    equivalent of 1 disk is used for parity
    checksum.
  • Parity checksum is used for error detection
    and to help recover / rebuild data in case of
    loss of 1 disk
20
Q

RAID 6

A

Striping with double parity

Can survive loss of 2 disks

21
Q

RAID 10 – Raid 0 + Raid 1

A

Splits into two halves (Raid 1)

  • Strips data across the disks in each half (Raid
    0)
  • Only half the total disk space is usable.
  • If one half is lost, data can be copied from the
    surviving half
22
Q

SAN acronym:

A

Storage Attached Network

23
Q

SAN definition

A

Designed for providing storage solutions to networked users.

Targeted at servers rather than clients*

Super high-speed, very low latency BUT super expensive

Enterprise level usage

24
Q
  • SANs usually runs on what cable? Speeds up to what amount?
A

fibre optic, hence 100s of videos can be used simultaneously with speeds of up to 10Gb/s

Easy to scale up, which is a major advantage over NAS

25
Q

Availability definition

A

Availability is the minimal interruption to service, i.e., minimal downtime

It is measured in 9s

26
Q

High Availability definition

A

High Availability is the percentage of time the network is available.

It is measured in 9s

27
Q

How many hours of downtime per anun with a network availability of 99.9%?

A

approx. 9 hours downtime per annum

28
Q

How many hours of downtime per anun with a network availability of 99.99%?

A

approx 1 hr downtime per annum

29
Q

How many hours of downtime per anun with a network availability of 99.999%?

A

approx 5 mins downtime per annum

30
Q

How many hours of downtime per anun with a network availability of 99.999999%?

A

approx. 316ms downtime per annum – AWS S3 storage

31
Q

Fault tolerance definition:

A

Fault Tolerance is the ability to withstand fault and continue to function as expected. Aka zero service interruptions.

Achieved using redundancy (back ups)

32
Q

Redundancy definition:

A

A fault tolerance method

Used for fail-over – where another takes over when the primary (active) fails

Hot-swappable – devices or components can be removed, added or replaced while the server is running.

Example mouse/kb.

Some high-end servers support hot-swappable disks, memory and even CPU * Hot-swappable is called “hotplug” in Linux world

33
Q

Server clutering

A

a type of redundancy

two or more servers configured to work together as a single entity.* Both are exact replica and can be running simultaneously or in active/passive mode

34
Q

Redundancy - load balancing

A

load balancing – where tasks are split across both servers, thus improving performance.

35
Q

raid is a form of

A

redundancy

COSC 118 (16 decks)

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