1. Cloud Computing Systems Lin Gu Hong Kong University of Science and Technology Sept. 21, 2011 Windows Azure—Overview

2. 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

3. 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

4. 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

5. Windows Azure Web & Worker Roles 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 Web Role Worker Role 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.

6. Azure Apps– Overview Storage Tables LBLB LBLB Blobs Worker Service Worker Role Managed Interface Call Worker Role Managed Interface Call Web Site (ASPX, ASMX, WCF) Web Site (ASPX, ASMX, WCF) Web Site (ASPX, ASMX, WCF) Web Site (ASPX, ASMX, WCF) Web Role IIS as Host Web Role IIS as Host Queues Windows Azure Data Center LBLB LBLB LBLB LBLB The Internet The Internet via TCP or HTTP

7. Azure Apps - Scale out

8. 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

9. 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

10. 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 Node Health Index Missed Heartbeats Heartbeat Interval Missed Heartbeat Recovery Initiated Heartbeat Timeout

11. 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