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What is virtualization?
-the creation of substitutes for real resources – abstraction of real resources
Example of virtualization
-Ex. SAN, VLAN, RAID
Advantages of virtualization:
- -Portable virtual machines
- -Consolidation of resources
- -Isolation of virtual machines
Disadvantages of virtualization:
-applications run faster
-the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network.
Storage virtualization (e.g. SAN)
-is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console.
- -A virtual machine is a tightly isolated software container that can run its own operating systems and applications as if it were a physical computer.
- -On a given h/w platform (host) – simulated (virtual) machine environments are created
Benefits of system virtualization:
- -consolidation to reduce hw costs
- -workloads consolidation
- -single consolidated view/management
- -portability of virtual machines
- -can be used for testing/training
What is virtual infrastructure?
-Is sharing of physical resources (servers, storage, network) as a dynamic resource pool
- -Type 2 hypervisor
- -host O/S runs virtualization software, unmodified guest O/Ss run isolated from each other (separate virtual machines)
- -Additional resources are required for host O/S
- -(type 1 hypervisor)
- - there’s no host O/S. Virtual machines run on top of type 1 hypervisor directly on a hardware platform
- -No resources are wasted for a Host O/S
- -Higher virtualization efficiency can be achieved
- -Guest O/S is modified to include a call to hypervisor to access h/w resources
- -Guest O/S is “aware” of running in a virtualized environment
- -Makes the structure of hypervisor simpler
- -May make virtual machine more efficient
Disadvantage of paravirtualization
-Guest OS is modified
Full (transparent) virtualization
-Refers to the process of allowing each guest operating systems run unmodified in isolation
Main challenges of transparent virtualization
-Guest OS privileged instructions expect to run in Ring 0
-Modifying a CPU to include extended set of instructions
Hardware-assisted virtualization technology affect virtualization software, such as Vmware by
-It complements it for more efficiency
Virtual Embedded Bridge (VEB)
-a software switch as part of the hypervisor
External Hardware Switch
-switching function performed by an external switch
What is Cloud Computing
-Dynamically scalable, device-independent and task-centric computing resources are provided online, with all charges being on a usage basis.
Some of Cloud Computing defining characteristics?
- -Apps (s/w), processing power and storage (h/w) accessed on the Internet, online
- -Task-centric computing
- -Device/platform independent computing
- -Dynamically scalable, on-demand computing
- -Resources are available with variable, per-usage costs (not fixed)
Advantage of cloud computing over traditional data center
- -Pay-per-use resources
- -Accessible from most devices
- -Promotes collaboration
Disadvantages of cloud computing
Example of cloud computing
- -A User creating a Facebook application
- -A user accessing a Yahoo email account
- -A user accessing a supplier's virtual server to test an application
- -Not an example
- --A user accessing his email account on their company's email server
The fact that cloud computing has no fixed costs makes it more attractive to small companies
- -Software as a Service (Saas)
- -Running existing online applications.
- -Online productivity tools, including word processing, spreadsheet, presentation: GoogleDocs, Zoho, Microsoft)
- -creative web tools - Pixlr, Jaycut, Aviary
- -dedicated business applications: Salesforce, Employease, NetSuite .
- -Available for free or as a subscription service, accessible from any Internet client, facilitate collaboration.
- -The disadvantage is that they are not customized enough, too generic.
A user accessing a cloud supplier's payroll application
-Example of SaaS
- -Platform as a Service (Paas)
- -Environment and a set of tools to create online applications,
- -Allows quick development of applications without much additional cost.
- -Can deploy applications privately or publicly.
- -Limits developers to an existing set of tools and languages and platform dependency.
Using a browser, you develop and run your ecommerce website and application on a supplier's server that runs Java-based programming tools
-Example of PaaS
- -Infrastructure as a Service (Iaas), sometimes known as Hardware as a Service (Haas).
- -Allows a business to run their own applications on the cloud hw without investing in its own hw infrastructure.
- -Cloud suppliers can use actual physical or virtual servers to host applications.
What are 4 types of IaaS?
-private, dedicated, hybrid and cloud hosting
-(certain physical servers are dedicated to one customer)
-(customer rents physical servers on demand as needed)
-(a mix of physical and virtual servers to reduce cost and increase flexibility)
-(customer rents virtual servers on demand as needed, sometimes hourly).
What are some of concerns and issues with Cloud Computing today?
- -Data theft/loss
What is caching?
- -Temporary storage of frequently accessed data (duplicating original data stored somewhere else)
- -Reduces access time/latency for clients
- -Reduces bandwidth usage
- -Reduces load on a server
-for a single user
(Proxy) Shared cache (forward and reverse)
-same principle for multiple users
Forward Proxy Caching
- -Cache located closer to the client
- -Usually deployed by an ISP
- -Decreases bandwidth usage (ISP to the Internet link in the example below)
Reverse Proxy Caching
- -Aka gateway proxy or web accelerators
- -Cache proxy located closer to the origin web server
- -Usually deployed by an Web hosting ISP
- -Decreases load on the web server
- -Several reverse proxy caches implemented together can form a Content Delivery Network
-how long the document stays “fresh” or can be used from cache without rechecking the origin server
-[seconds] — specifies the maximum amount of time that an representation will be considered fresh.
-tells all caches how long the associated representation is fresh for
- – compare the cached document to the origin document once it’s not “fresh” anymore
- -Are used by caches to compare the cached document to the original document for changes
- -If validator is not present and no freshness information is available, the document won’t be cached
-the last time that the document last changed
-unique identifiers that generated by the server and changed every time the representation does
- – done by switches/routers, clients are unaware
- -To avoid configuring each client to point to cache proxy
- -Can be accomplished using inline cache, layer 4 switch, WCCP, policy-based routing
- -Cache pretend to be the origin server, tricks client into thinking it's connected to the server
Content Delivery Networks
- -Network of computers that deliver content on the web.
- -Content pushed-out/delivered “closer” to the clients
- -Designed to improve Internet performance (i.e. decrease latency for clients, decrease bandwidth use)
- -Consists of origin server, surrogate (edge servers)
- -Caching and server load balancing techniques are used
- -ESI (Edge-Side Includes) – open standard markup language to augment HTML for help with dynamic delivery and assembly of Web documents
Benefits of Content Delivery Networks
- -Designed to improve Internet performance
- -(i.e. decrease latency for clients, decrease bandwidth use)
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