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Cloud Computing > 2 - Data Centre Arch & Management > Flashcards

2 - Data Centre Arch & Management Flashcards

1
Q

Logically, where are datacentres on the internet?

A

In the core

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2
Q

What do data centres peer with

A

ISPs and Internet eXchange Points

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3
Q

Data centres have rows of …

A

racks

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4
Q

Problems with blade servers in higher density

A

Require more power
Requrie better cooling
Require larger bandwidth

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5
Q

Block Storage

A

Data stored in fixed size blocks.
Several blocks build a file
Each volume can be treated independently
Managed by OS

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6
Q

Object Storage

A

Data file with corresponding metadata
Each object has a Unique ID
Stored across all disks in array
Managed by application not OS

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7
Q

DAS

A

Directly Attached Storage

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8
Q

In which context do hard drives work best?

In terms of data NOT anything else

A

Sequential accesses (over random)

Due to the mechanical movement of the arm

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9
Q

How much per server storage is generally used? and for what?

Relatively - not looking for any numbers

A

Little. Only for boot and swap etc

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10
Q

NAS

A

Network Attached Storage

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11
Q

SAN

A

Storage Area Network

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12
Q

What does SAN provide?

A

Block-oriented storage that resides across a network

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13
Q

What networking tech does SAN traditionally use?

A

Fibre Channel (SAN Switch)

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14
Q

What are the 4 typical types of network accesses/physical networks in data centres?

A

Client-server
Server-server
Storage access
Management

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15
Q

InfiniBand

A

Commonly used in supercomputing for physical connection also in large datacenters for switching backbone

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16
Q

InfiniBand material

A

Copper or fibre

17
Q

InfiniBand bandwidth

A

1Gbps, 10 and 40 (100 being introduced)

18
Q

Routers

A

Connect networks to the internet
Expensive

19
Q

Switches

Definition and port density

A

Interconnect data centre devices.
High port density, 48 ports are common

20
Q

Middleboxes

A

Provide additional services between router/switch.
Low port density
Operate on Layer 4-7

21
Q

In terms of cost, why are hierarchical networks used in data centres?

A

Equipment higher up more traffic = more expensive

22
Q

High end or low end server:

memory or IO bound apps

A

Low end

23
Q

Parallelisation

A

Splitting a computational task into separate packages
then assigning each package to a node for processing.

The results are then aggregated.

24
Q

Why might it NOT be preferable to use single core, single processor servers in clusters?

A

Reducing serialisation and communication overheads becomes increasingly difficult
Load balancing becomes harder - hard to predict response times
Highly parallel programs are hard to write

25
Q

How many chassis does each rack hold? How many Us per rack?

A

4 Chassis per rack, each can hold 16u.

26
Q

How does DAS work

A

Directly attached to the server using USB, SATA etc.

27
Q

NAS vs SAN

A

NAS manages its own storage and is a file/object level solution, also accessible to anyone.

SAN has block level access to pools of virtualised storage that are accessible to everyone.

28
Q

NAS Downsides

A

High latency (ethernet)
Low Bandwidth ^
High Level file access not suitable for some apps (database management)

29
Q

What is fibre channel networking

Prompt: protocol

A

High-speed data transfer protocol providing in-order, lossless delivery of raw block data.

30
Q

What is Fibre Channel used to connect?

A

Connect storage to servers in storage area networks in commercial data centers

31
Q

Downsides to FC networking

A

Need separate infrastructure and specialised network admins (expensive)

32
Q

Middlebox use examples

A

Load balancer
NAT
Firewall
Intrusion detection system

33
Q

Hierarchical Network

What they provide and how they are connected

A

Provide Redundancies, high bandwidth and fault tolerance
Servers connect to top of rack switches (1-10Gbps), these connect to layers of aggregation switches.

34
Q

Execution time formula

A

execution time = 1ms+f(100ns/n +100ns(1-1/n))
n= number of nodes
f= the number of global accesses per 1ms work unit

35
Q

Advantages of low end servers

A

Cheaper per server
Higher memory bandwidth/IO to compute ratio (better for io bounded applications)

36
Q

Why are datacenters ideal for parallelisation

A

Large collection of affordable servers & storage
Large high speed data interconnects between servers

37
Q

Challenges of Data center management

A

Managing and provisioning resources
Managing and detecting faults
Programming
Debugging

38
Q

In data center management, what do you need an operating system for?

A

Resource management, utilisation and health monitoring
Deployment and maintenance
Programming framework support

39
Q

Data center management operating system

A

Open Stack

Cloud Computing (10 decks)

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