Revision as of 16:36, 27 January 2015

Notes for the first session that happened on Jan. 5th, 2015.

Course Outline

Undergrad Grading Scheme

15% Class Participation
15% Reading Responses
10% lecture Notes/Wiki Contributions
25% Midterm
35% Final Exam

Grads Grading Scheme

15% Class Participation
15% Reading Responses
10% Lectures Notes/Wiki contributions
10% Project Proposal
15% Project Presentation
35% Final Project

Project

A literature review of distributing operations
Research proposal on a problem related to distributed systems

Discussion

Q: What do you think of when you hear 'Distributed System'?

Group 1

Sharing Resources
Spreading Work Loads
Scheduling
Process migration
Different nodes have different purpose
Google
Parallel running processes
Nodes
Resource Allocation across multiple nodes
Scheduling multiple nodes
Resources availability among nodes
Problem: across multiple machine

Group 2

Request comes from (usually) one computer and processing is usually handled by more than one computer
Tasks are divided into small parts which can be processed individually before coming back together
Usually deals with large scale data sets
Globalization
Fault tolerance
Usually emphasize distributed agents to not work on certain schedule
Examples: Map Reduce, cloud, cloud software (Google Drive)

Group 3

Separated, networked machines
Coordinated by similar or identical software
Error recovery/redundancy
No controlled storage
Coordinated communication facilitating operation on coordinated task
Leader/hierarchy for task delegation

Group 4

Distributed, multiple systems
OS: The root level system that operates a computer system
Dist. OS more complexity

Prof Discussion Notes

Key words: network, parallel, fault tolerant, redundancy, complexity

Distributed OS is kind of OS

But what is an OS in the first place?

Connection software and hardware
Resource allocation
Abstraction layers
Makes it easy to run higher level programs on different computers
Sharing: resources are split up and each process is isolated, this improves security and programming (no need to worry about sharing)
Virtual memory, process scheduling

What is a distributed system?

Focused on "network transparency", in order to provide to the user the sense that he/she interacts with a single machine as if all the resources were local.
Do the things users take for granted on regular computers
Does not scale relatively to the number of resources in the system (i.e.: 100 computers, does not equal a distributed system that is 100 times faster than a single computer)
In a way, opposite of an operating system: instead of splitting up a single computer into many, it takes many and tries to merge into one
Resources can be divided as you want
Centralized control solves some issues, but has issues of its own
Since it cannot truly act as a single computer, we fake it as much as possible - and it works in some scenarios
The more specialized the task, the better it will scale (i.e.: grid computing with very specific computations that are heavily parallel in nature)
Interact it, process update, callback,
Gmail so responsible - it perfected , downloads in your browser
Cache - they predict what the processor going to do

Distributed Operating System represented as a Venn diagram. OS denotes an operating system, and DS denotes a distributed system. The black center represents a distributed operating system; a system with properties of an operating system and a distributed system.

Operating System Examples

Mobile devices - Phones

iOS
Android

Embedded OS

Linux
QNX
xBSD firewalls

Desktop

Windows
OSX
Chrome OS

Server

Windows
Linux
BSD

Main Frames

OS/400

Is the cloud an OS? Important question.

Cloud

MPI
AWS
Google App Engine

No, they are at best proto-OSs because the abstractions they provide are very leaky. They only provide limited APIs.

--> I do not agree, it really depends on how expansive is your definition of cloud... (i.e.: IaaS provides the ability to the user to spin a full fledged OS on a VM (for which you have no explicit idea of the physical architecture, it could be part of a 96 SBC server-rack connected to dedicated HDD/SDD server-rack, etc.) ) Again this is semantics, but I feel we need to clarify the terminology.

Pick a system and show how it is and is not an OS

Group 1

**BOINC**
Similarities to a traditional OS	Differences from a traditional OS
Very parallel	Can handle only very specific (trivially parallelizable) types of problems
Availability	Abstraction layer is poor
Scheduling
Networked
Nodes may come and leave as they like (it is active when the computer is idle)
Same problem at the same time
Redundant/Fault tolerant
Allocation can be handle by system
Large problem managed by one system
Anyone can submit projects

Group 2

**Facebook**
Similarities to a traditional OS	Differences from a traditional OS
OK abstraction (for human communication/control)	Doesn't really take a single resources and split it up into smaller ones
The programming API is stable	The human API (user interface) is not stable
Able to separate resources such as wall posts, photos, etc	Limited control

Group 3

**Google Docs (Drive)**
Similarities to a traditional OS	Differences from a traditional OS
Has a file system	Somehow still not a true OS
Provides hardware abstraction (users don't care how the requests are carried out)
Has an API

Group 4

**LinkedIn**
Similarities to a traditional OS	Differences from a traditional OS
Supports multiple location/users	Specific functionality (not abstract)
Multiple servers around the world
Resource/Security management
Networked
Cross-platform (Desktop/Mobile)