1. Virtualization and the Cloud
Chapter 7 ++
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

2. Virtual Machines : History
The structure of VM/370 with CMS.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

3. Simplified structure of a microkernel system
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

4. Virtual Machines Rediscovered
From IBM:
Hardware partitioning subdivides a physical server into fractions, each of which can run an operating system. These fractions are typically created with coarse units of allocation, such as whole processors or physical boards. This type of virtualization allows for hardware consolidation, but does not have the full benefits of resource sharing and emulation offered by hypervisors. Hypervisors use a thin layer of code in software or firmware to achieve fine-grained, dynamic resource sharing. Because hypervisors provide the greatest level of flexibility in how virtual resources are defined and managed, they are the primary technology of choice for system virtualization.
There are two types of hypervisors.
Type 1 hypervisors run directly on the system hardware. The following figure shows one physical system with a type 1 hypervisor running directly on the system hardware, and three virtual systems using virtual resources provided by the hypervisor.
Type 2 hypervisors run on a host operating system that provides virtualization services, such as I/O device support and memory management. The following figure shows one physical system with a type 2 hypervisor running on a host operating system and three virtual systems using the virtual resources provided by the hypervisor.
Paravirtualization – presents machine like software interface that explicitly exposes the fact that it is a virtualized environment. It offers hypercalls which lets OS request from hypervisor
Paravirtualization
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

5. Virtual Machines Rediscovered
(b)
From IBM:
Hardware partitioning subdivides a physical server into fractions, each of which can run an operating system. These fractions are typically created with coarse units of allocation, such as whole processors or physical boards. This type of virtualization allows for hardware consolidation, but does not have the full benefits of resource sharing and emulation offered by hypervisors. Hypervisors use a thin layer of code in software or firmware to achieve fine-grained, dynamic resource sharing. Because hypervisors provide the greatest level of flexibility in how virtual resources are defined and managed, they are the primary technology of choice for system virtualization.
There are two types of hypervisors.
Type 1 hypervisors run directly on the system hardware. The following figure shows one physical system with a type 1 hypervisor running directly on the system hardware, and three virtual systems using virtual resources provided by the hypervisor.
Type 2 hypervisors run on a host operating system that provides virtualization services, such as I/O device support and memory management. The following figure shows one physical system with a type 2 hypervisor running on a host operating system and three virtual systems using the virtual resources provided by the hypervisor.
Paravirtualization – presents machine like software interface that explicitly exposes the fact that it is a virtualized environment. It offers hypercalls which lets OS request from hypervisor
A type 1 hypervisor.
A practical type 2 hypervisor
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

6. Requirements for Virtualization
Hypervisors should score well in three dimensions:
Safety: hypervisor should have full control of virtualized resources.
Fidelity: behavior of a program on a virtual machine should be identical to same program running on bare hardware.
Efficiency: much of code in virtual machine should run without intervention by hypervisor.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

7. Type 1 and Type 2 Hypervisors (1)
Location of type 1 and type 2 hypervisors.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

8. Virtualizing the Unvirtualizable
The binary translates rewrites the guest operating system running in ring 1, while the hypervisor runs in ring 0
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

9. Virtualization Technology
2005 – Intel CPU’s introduced Virtual Technology (VT)
Containers are created in which virtual machines can be run.
I/O instructions, etc, Trap in the hypervisor who does the work on behalf of the virtual machine.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

10. Techniques for Efficient Virtualization
When the operating system in a virtual machine executes a kernel only instruction, it traps to the hypervisor if virtualization technology is present.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

11. Memory Virtualization
Hypervisor creates a shadow page table that maps virtual pages used by virtual machines to actual pages the hypervisor gives it.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

12. Hardware Support For Nested Page Tables
Extended/nested page tables are walked every time a guest physical address is accessed—including the accesses for each level of the guest’s page tables.
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

13. Memory Virtualization
Reclaiming memory
Hypervisor pretends that the total memory for all VMs combined is more than the actual memory.
Deduplication : Pages sharing the same content are shared.
Ballooning : A small balloon module is loaded in the VM as a pseudo device driver that talks to the hypervisor.
inflates – memory scarcity on guest increases
deflates – more memory becomes available for guest
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

14. I/O Virtualization
Problem: Each guest thinks it owns an entire disk partition.
Hypervisor creates a file or region and gives it to the OS
Problem: the disk the guest OS is using is different from the real one.
Hypervisor converts disk commands to drive the real disk
Allows upgrades to hardware without changing software.
Problem: Networking link for each guest OS
Each VM has its own MAC address
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

15. Networking Switch Virtual LAN Virtual LAN Host B Host A Bridge Bridge
/24
02:01:0A:00:02:01
/24
02:01:0A:00:01:03
/24
02:01:0A:00:02:02
/24 vm vm vm vm vm
02:01:93:60:51:f1
157.96,81,241/24
Bridge
Virtual LAN
PUBLIC ACCESS
Internet

16. I/O Virtualizations
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

17. Shrink wrapped virtual machines used for product solutions
Virtual Appliances
Shrink wrapped virtual machines used for product solutions
Licensing Issues
License contracted to one physical machine?
Virtual Machine?
All virtual machines on one physical machine?
What about licenses to multiple machines?
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

18. Virtual Machines on Multicores
Read text
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

19. Short video intro

20. Model for enabling the delivery of computing as a SERVICE.
Defining the Cloud
Model for enabling the delivery of computing as a SERVICE.

21. Clouds
National Institute of Standards and Technology defines characteristics of “cloud”
On-demand self-service
Broad network access
Resource pooling
Rapid elasticity
Measured service
Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.

22. Service Models SaaS PaaS IaaS Software as a Service
Platform as a Service
Infrastructure as a Service
SaaS
PaaS
IaaS
NIST Definition

23. Cloud computing layers

24. Deployment Models Public Cloud Private Cloud Hybrid Cloud
Community Cloud
NIST Definition

25. Infrastructure Management
IaaS is the delivery of computer hardware as a service
Servers
Networks
Storage
IaaS

26. Virtual Machine Monitor (Hypervisor)
Virtualization
VIM: Virtualization Infrastructure Management H
HOST
Web Server DB
Server
Facebook app DB
Java
App A
App B
App C
Window
Linux
Guest OS
Manage the physical and virtual resources in a holistic fashion.
Rapidly and dynamically provision resources to applications
Virtual Machine Monitor (Hypervisor)
HARDWARE
IaaS

27. Client Migration Services Cloud Interface VM6 VM1 VM 4 VM7 VM5 VM 2
Migration services is the process of moving a virtual machine from one host server or storage location to another.
Used to:
Make adjustments to resource priorities to match demand conditions
Service upgraded
Migration Services

28. Migration Services IaaS
All key machine’s components, CPU, storage disks, networking and memory are completely virtualized. This facilitates the entire state of the virtual machine that must be captured and moved.
Various techniques:
Live (hot or real time) migration : VM is powered on
Regular (cold) migration: VM is powered off
Live Storage migration
IaaS

29. PaaS: Platform as a Service
There isn’t one approach to PaaS.
The line between Iaas and Paas is blurred
Common PaaS Characteristics:
Offers development environment
Development lifecycle, language
Ability to develop, test and deploy applications
Customer uses this to add value
Support well-defined interfaces for:
Composite applications
Portals
Mashups (brings together 2 or more business apps)
Based on multi-tenancy architecture
From Wikipedia:
Multitenancy refers in software architecture where a single instance of the software runs on a server, serving multiple client-organizations (tenants). Multitenancy contrasts with multi-instance architectures where separate software instances (or hardware systems) operate on behalf of different client organizations. With a multitenant architecture, a software application is designed to virtually partition its data and configuration, and each client organization works with a customized virtual application.
Commentators regard multitenancy as an important feature of cloud computing.[
Virtualization
The costs of redesigning applications for multitenancy can be significant, especially for software vendors who continue to offer an on-premise single tenant version of their product. They end up being forced to support 2 distinct products with all the resulting costs.
An increasingly viable alternative route to multitenancy that eliminates the need for significant architectural change is to use virtualization technology to host multiple isolated instances of an application on one or more servers. Indeed, when applications are repackaged as virtual appliances the same appliance image can be deployed in ISV hosted, on-premise or trusted-third party locations and even migrated from one deployment site to another over time.
PaaS

30. Enabling Technologies
Provides a specialized capability, such as a tool or tool set Ex. Amazon’s Simple DB and Simple Query Service
PaaS

31. SaaS: Software as a Service
30 years ago…… Time-sharing systems ….. SaaS model today motivated by Faster, ubiquitous networked communications Software costs and complexities IT costs
SaaS

32. Packaged Software SaaS
Focus on a specific process, such as performance reviews, financial management…
Moved to the cloud because customers are finding the platforms hard to manage
Characteristics
Designed with a specific business processes build in
Modifiable by customers
Examples: Intuit, SAP, Oracle On Demand
SaaS