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

Course Outline

Undergrad Grading Scheme

Grads Grading Scheme

Discussion

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)

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

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

Mobile devices - Phones

Embedded OS

Desktop

Server

Main Frames

Is the cloud an OS? Important question.

Cloud

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

**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

**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

**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

**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)