Card Set Information
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
-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
-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
-Accessible from most devices
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?
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)