Cloud Computing Systems

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Cloud Computing Systems
Windows AzureOverview

• Lin Gu

Hong Kong University of Science and Technology
Sept. 21, 2011
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Cloud Systems

• Infrastructure as a Service (IaaS) basic
  compute and storage resources
• E.g., Amazon EC2, VMWare vCloud
• Platform as a Service (PaaS) cloud application
  infrastructure
• E.g. Google App Engine, Salesforce.com, Windows
  Azure
• Software as a Service (SaaS) cloud applications
• E.g. Google Docs, Microsoft Office Web
  Companions, Office 365

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Windows Azure - Overview

• Windows Azure is a platform for cloud-based
  application development
• For the datacenter parallel processing, resource
  management, provisioning, and monitoring
• For users cloud-based applications, integrated
  development environment

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Application Model

• Cloud apps are constructed in role-instance Model
• A role instance is a set of code, configuration,
  and local data, deployed in a dedicated VM
• At runtime each Role executes on one or more
  instances

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Windows Azure Web Worker Roles
Web Role
Worker Role

• Customized for web applications
• A web role is a worker role with the addition of
  IIS (i.e., it can do everything a worker role can
  do as well)

• For general development and computation
• Background processing

Windows Azure currently supports two types of
roles worker role and web role. A service must
include at least one role of either type, but may
consist of any number of web or worker roles.
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Azure Apps Overview
The Internet
The Internet via TCP or HTTP
LB
LB
LB
Storage
Windows Azure Data Center
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Azure Apps - Scale out
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How Azure runs an app

• The Fabric Controller
• Process app definition files to create VHDs
  (Virtual Hard Disks)
• Place role VHDs on compute nodes
• Boot and configure role instance VMs
• Start role host processes (IIS, WCF)
• Run role instances
• Response to HTTP request
• Maintain service health

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Node Structure

• A node is a management unit of FC
• Contains an FC Agent in Hyper-V root partition
• Each role instance runs in Guest OS with GA
• FA delegates GAs to handle VM status

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Node Health Monitoring

• Based on heartbeats, which are typically sent in
  15 second intervals
• Once the index falls below zero, FC attempts to
  heal node
• For example, host agent timeout is 10 minutes
• Timeouts vary depending on node state and
  operation
• Worst-case reaction time is timeout interval
  heartbeat interval

Missed Heartbeats
Missed Heartbeat
Recovery Initiated
Node Health Index
Heartbeat Interval
Heartbeat Timeout
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Windows Azure Storage

• The Windows Azure storage services provide
  storage for binary and text data, messages, and
  structured data
• Blob service storing binary and text data
• Queue service storing messages that may be
  accessed by a client
• Table service structured storage for
  non-relational data
• Windows Azure drives mounting an NTFS volume
  accessible to code running in your Windows Azure
  service
• Programmatic access to the Blob, Queue, and
  Table services is available via the Windows Azure
  Managed Library and the Windows Azure storage
  services REST API

-- http//msdn.microsoft.com/library/ee924681.aspx