308 lines
11 KiB
Markdown
308 lines
11 KiB
Markdown
# SLA and Virtualization
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## SLA
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### Definition
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- Service Level Agreement: a service-based legal agreement between a
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**provider** and a **subscriber**
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- Accepted before a cloud service can be used
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- Content
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- Provider's responsibility
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- Subscriber's responsibility, and entitlements
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- Billing and accounting system
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### Types
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- Service based SLA:
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- Offer shared resources, used by many customers
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- Offered to cloud users
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- Customer based SLA
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- Agreement between individual customer or group, to provide non-shared
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**specific** services
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- Multi-level SLA:
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- Corporate level: generic and cover all user of an organization
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- Customer level: specific group of user
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- Service: specific type of service
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### Boundaries
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- Organizational boundary
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- Physical perimeter, owned and governed by organization or cloud provider
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- Trust boundary
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- When cloud user extend trust beyond its physical boundary, and include
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resources from the cloud
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### Characteristics of cloud
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- On-demand usage: use more cloud resources only when they need it
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- Multi-tenancy aka. Resource pooling: Resources are **instances** that can be
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used by many users
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- Scalability: Able to automatically scale up or down based on the settings and
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agreements
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- Ubiquitous access: Can be accessed everywhere with lots of devices
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- Measured usage: keep track and record the amount of IT resources used by
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consumers
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- Used for accounting and auditing
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- Resilience: distribute and replicate resources to provide redundancy, and fail
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over mechanism
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### QoS
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- SLA is based on **Quality of Service**
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- Combination of metrics relating to requirements, and satisfaction of services
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offered by a provider.
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- Quantitative or qualitative
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- Parameters:
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- **Reliability** availability
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- **Security** and trust
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- **Scalability**
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- **Data** integrity and data protection
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- **Resilience**
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- Data **recovery** time
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- Support
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## Virtualization
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### Definition
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- The process of creating the **virtual** version of hardware, database,
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operating system and application from real copies, using virtual machine
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**monitor** to emulate the physical functionalities.
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- Multiple virtual machines are **multiplexed** in to the same hardware, to
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serve as an abstraction of physical OS
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- Guest OS is not bound to the physical hardware.
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- **Guest** OS runs on **host** OS, and they can be different
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### Levels of virtualization
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- Instruction Set Architecture level: ISA **emulation**, which is used to run
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many legacy codes written for a different hardware configuration, like
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_Dynamo_
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- Hardware level: VMs are located directly on top of **hardware**, allows the
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virtualization of each of the hardware components, which could be the
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input-output device, the memory, the processor, etc, like _VMWare_
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- Operating system level: an operating system (OS) virtualization paradigm in
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which the kernel allows the existence of multiple isolated user space
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instances, like _Jails_
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- Library level: translate API calls to user libraries, like _vCUDA_
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- Application level: allows high-level language programs to be compiled easily.
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java's _jvm_
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### Types of Virtualizations
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- Desktop: Create desktop computer from physical desktop machine
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- Hardware: Virtual computer with OS that represents and act as a real physical
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computer.
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- Nested virtualization: Virtual machine inside another one
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- CPU virtualization: Virtual CPU are created to reduce stress on host
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- Memory virtualization: virtual memory is created and run on the VM, controlled
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by the virtual CPU of VM, but can't access memory address outside virtual
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- IO virtualization: Route IO request between virtual devices and physical
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hardware
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### Virtual clusters
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- Physical cluster: interconnected by physical network
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- Failure may cause a falling physical node
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- Virtual cluster: VMs intereconnected by a virtual network across several
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physical networks
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- Node can be either physical or virtual
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- Cluster VMs can run different OS
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- To enhance **utilization** and **flexibility**
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- Can be freely replicated, and is **fault** tolerant easy to recover
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- Nodes can grow or shrink
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- Failure won't cause shutdown to host machine
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### Migration of VM
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#### Introduction
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- VM can be moved from one cluster to another, which **isn't possible** with
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physical hosts.
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- Four ways:
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- Guest-based manager, where cluster manager is in guest vm
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- Host based manager: supervises the guest system, and can restart guest
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system remotely
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- Independent cluster manager on both host and guest
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- Use integrated cluster manager
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#### Six (five) steps of VM migration
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- Start migration (for some reason this is counted as step 0 and 1???)
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- Determine VM to migrate
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- Determine destination host
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- Transfer memory
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- State is stored in memory, so transfer memory first
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- Suspend VM and copy remaining data
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- Execution is suspended when last memory is transfered.
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- Non memory components like network and cpu are sent to destination
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- Commit
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- After all data, VM reloads and continue execution
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- Activate
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- Network is redirected to new VM
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- remove the original VM from source host
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### Mechanism for cloud infra: building blocks
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- Environment:
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- Logical network perimeter: Virtual network boundary, encompass and isolate
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a group of resources, that may be **physically** distributed., to _isolate
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cloud resource from unauthorized users_
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- Virtual Server: behaves exactly like a physical one, and running on the
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same physical server which is shared by multiple cloud users
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- Resource replication: create multiple of same resource to various
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locations, physically distributed around the world.
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- Ready made environment: provided by PaaS (platform as a service)
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- Failover system: use clustering to provide redundancy
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- Hypervisor: generate virtual server instances
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- Multi device broker: converts and exchanges information
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- Resource cluster: cloud resources are geographically distributed and group
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resources and instances together
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- State management database, used to temporarily maintain state data for
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software programs to improve performance.
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- Scaling
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- Automated Scaling listener: monitors communication between consumers and
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services for dynamic scaling up or down.
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- Load balancer: cloud runtime mechanism that distributes workload: data
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processing, computation, network traffic across two or more cloud
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resources, for better performance( automated horizontal scaling)
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- Monitoring
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- Cloud usage monitor: Autonomous software used for collecting and
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processing cloud resource usage data.
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- SLA monitor: monitors the performance to ensure they are fulfilling the
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Quality of Service requirement
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- Pay per use monitor: monitor the usage and calculate the price according
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to the agreement
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- Audit monitor: track data for network, to confirm to regulatory obligation
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### Different hypervisors
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#### Microsoft virtualization technology
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- parent partition: logical hard drive for running hypervisor layer, and nesting
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child partitions
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- Child partitions: Logical hard drive responsible for running isolated OSes
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- Virtualization stack Collections of resources including the hypervisor, which
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makes up the Microsoft hyper V
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- Virtualization service provider: parent partition side, server that handles IO
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- Virtualization child provider: child partition component, that sends request
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to VSP
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- VMBus: send requests and data between VMs
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- WMI: Windows management instrumentation, manages virtual devices
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- Windows kernel: manages IO request from parent and child
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- IHV: hardware drivers
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- VM worker process: run and configure one VM each
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- Hypervisor
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- Manages a minimum set of **hardware** components
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- **Isolate** component, to enhance **loose coupling**
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- Provide **security**
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- Enhance **performance**
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- 
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#### Xen Virtualization Technology
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- 
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- Host Hardware: real hardware
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- Xen Hypervisor: lean software layer, that runs on **host hardware** and
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manages the **CPUs, memory, IO devices**
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- Guest Domains / Virtual Machines
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- Control Domain, or domain 0: special virtual machine with privilege to access,
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and handles IO functions and VM's interactions
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- Toolstack: control stack on domain **0**, enables user to manage **virtual**
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machines
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### Virtualization Technologies
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- host components: real hardware
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- guest components: virtual system created from host machine, includes os,
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network, databases and servers
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- Hypervisor, or virtual machine manager: manages virtual machines
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- Networking technologies
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- Web services: manager over the internet
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- Front end systems: interface between user and virtual machine
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### Advantages and challenges
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#### Advantages:
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- Deployment:
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- Less **cost**, reduction in cost of hardware, energy, cooling , expertise
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and administration
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- Less time needed
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- Creating servers on different system is **easy**
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- Maintainence:
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- **Scalability**
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- **Efficiency**
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- **Reliability**
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- Fast data disaster **recovery**
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- Backups and migrations are **easy**
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#### Challenges
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- **Security** of virtual machines
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- Need **expertise** to manage virtual machines
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- **Reliant** back up systems are needed
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- Failures of **host** will affect the guest system.
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- **Performance** may not be as good as using physical ones
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### Future of Virtualization
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- Is and will be the **dominant** component of cloud computing
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- Decoupling of application will **increase**
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- **Less** energy consumption by optimizing OS and VMM
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- **Dominant** in IT market
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- Even more **scalable**
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- Better **security**
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### Major classes of hardware virtualization
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#### Full virtualization, Hardware virtual machine
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- Complete simulation of actual hardware, so that OS and software doesn't need
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any modifications.
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- AWS Support
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- HVM AMI (Amazon Machine Images), in a fully virtualized environment
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- Can run OS without modification
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- HW extension is support
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- Instance type support: all current
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- Regioin: all
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#### Paravirtualization
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- Allows guest applications to be executed, as if they are running on a separate
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system, but hard ware environment is not simulated
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- Guest need to be modified
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- AWS Support
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- PV AMI: special bootloader is used
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- Can run on host hardware without explicit support for virtualization
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- Hardware extention is not supported
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- Some instance types are supported
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- Some regions are supported
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### Layering and Virtualization
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#### Layering
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- Definition: approach to manage system complexity
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- Goals:
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- Simplify description of subsystem, to **abstract through interface**
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- Minimize interaction between subsystems
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- Enable us to independently manage each subsystem
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- Layering in computers:
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- Hardware
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- Software
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- OS
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- Library
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- Applications
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#### Interfaces in virtualization
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- ISA (Instruction Set Architecture): Instruction Set Architecture: boundary
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between hardware and software
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- ABI (Application Binary Interface): Allow application and library modules to
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access hardware, invokes **system calls**
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- API (Application Program Interface): Is a set of rules or protocols that
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enables software applications to communicate with **each other** to exchange
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data, features and functionality
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