Card Set Information

2014-04-22 01:17:09

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  1. What is virtualization?
    -the creation of substitutes for real resources – abstraction of real resources
  2. Example of virtualization
    -Ex. SAN, VLAN, RAID
  3. Advantages of virtualization:
    • -Portable virtual machines
    • -Consolidation of resources
    • -Isolation of virtual machines
  4. Disadvantages of virtualization:
    -applications run faster
  5. Network virtualization
    -the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network.
  6. 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. 
  7. System virtualization
    • -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
  8. 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
  9. What is virtual infrastructure?
    -Is sharing of physical resources (servers, storage, network) as a dynamic resource pool
  10. Hosted hypervisor
    • -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
  11. Bare-metal Hypervisor
    • -(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
  12. Paravirtualization
    • -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
  13. Disadvantage of paravirtualization
    -Guest OS is modified
  14. Full (transparent) virtualization
    -Refers to the process of allowing each guest operating systems run unmodified in isolation
  15. Main challenges of transparent virtualization
    -Guest OS privileged instructions expect to run in Ring 0
  16. Hardware-assisted virtualization
    -Modifying a CPU to include extended set of instructions
  17. Hardware-assisted virtualization technology affect virtualization software, such as Vmware by
    -It complements it for more efficiency
  18. Virtual Embedded Bridge (VEB)
    -a software switch as part of the hypervisor
  19. External Hardware Switch
    -switching function performed by an external switch
  20. What is Cloud Computing
    -Dynamically scalable, device-independent and task-centric computing resources are provided online, with all charges being on a usage basis.
  21. 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)
  22. Advantage of cloud computing over traditional data center
    • -Pay-per-use resources
    • -Accessible from most devices
    • -Promotes collaboration
  23. Disadvantages of cloud computing
    -Faster access
  24. 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
  25. The fact that cloud computing has no fixed costs makes it more attractive to small companies
  26. SaaS
    • -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.
  27. A user accessing a cloud supplier's payroll application
    -Example of SaaS
  28. PaaS
    • -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.
  29. 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
  30. IaaS
    • -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.
  31. What are 4 types of IaaS?
    -private, dedicated, hybrid and cloud hosting
  32. Private cloud
    -(certain physical servers are dedicated to one customer)
  33. Dedicated hosting
    -(customer rents physical servers on demand as needed)
  34. Hybrid hosting
    -(a mix of physical and virtual servers to reduce cost and increase flexibility)
  35. Cloud Hosting
    -(customer rents virtual servers on demand as needed, sometimes hourly).
  36. What are some of concerns and issues with Cloud Computing today? 
    • -Availability
    • -Privacy
    • -Data theft/loss
    • -Security
  37. 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
  38. Browser cache
    -for a single user
  39. (Proxy) Shared cache (forward and reverse)
    -same principle for multiple users
  40. 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)
  41. 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
  42. Freshness
    -how long the document stays “fresh” or can be used from cache without rechecking the origin server
  43. max-age
    -[seconds] — specifies the maximum amount of time that an representation will be considered fresh.
  44. Expires)
    -tells all caches how long the associated representation is fresh for
  45. Validation
    • – 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
  46. Last-Modified
    -the last time that the document last changed
  47. ETag
    -unique identifiers that generated by the server and changed every time the representation does
  48. Interception Caching
    • – 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
  49. 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
  50. Benefits of Content Delivery Networks
    • -Designed to improve Internet performance
    • -(i.e. decrease latency for clients, decrease bandwidth use)