1 / 16

OUTLINE

OUTLINE. INTRODUCTION VIRTUAL DISK PROXY VIRTUAL DISK CACHE CACHE HIERARCHY VIRTUAL DISK SERVER JAVA VIRTUAL MACHINE CDN STORE PROXY. INTRODUCTION.

verna
Download Presentation

OUTLINE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. OUTLINE • INTRODUCTION • VIRTUAL DISK PROXY • VIRTUAL DISK CACHE • CACHE HIERARCHY • VIRTUAL DISK SERVER • JAVA VIRTUAL MACHINE • CDN • STORE PROXY

  2. INTRODUCTION Virtual disk proxy is implemented along with VDC. VDC store objects that receives large fraction of request. And uses approximation for storing other objects. Cache hierarchy is used to fetch the object from neighboring caches or parents. VDProxy handles all network communication with VDServer. It provides interface to store for an operation read/write of pages. It opens socket connection to VDC & write commands indicating read & write operation.

  3. Virtual Disk Proxy

  4. Virtual Disk Proxy • It handles all the network communication with the VDServer. • VDC talks to the Disk Proxy module on one end and VDS on the other • VDC maintains hash table for the pages.

  5. Virtual Disk Proxy(cont’d) • VDC will request a page form the VDS if there is no page entry for the page. • A client sends a request to a cache, & if cache contains data requested, it replies with the data. Otherwise, it may ask it’s neighbors for the data, but if none of the neighbor possess the data, then it sends request to it’s parent in hierarchy.

  6. Virtual Disk Cache • Cache system defines hierarchy of data caches. • It checks for the request whether it may be able to satisfy it or some other will. If not, the request is made to parent cache. • Each cache independently decides whether to fetch references from objects home page or from sibling caches or parent caches using simple “resolution protocol ”.

  7. PROXY SERVER • It is a special program, launched on one of the computers, for which sizeable disk space is allowed. • VDS implemented in JAVA . • VDS has 2 threads ProducerThread & ConsumerThread.

  8. Proxy Server (cont’d) • ProducerThread listen network socket for Datagram packets. • The IndirectionMap simply handles a file that stores(address,allocation,entry)tuple. • Proxy Servers solves about 50% of all queries using it’s own disk. • These are available for Zenon/inter networking subscriber using dialup contracts.

  9. Java Virtual Machine (JVM) • In its standard form JVM is interpreter for bytecode. • Bytecode is optimized set of instructions designed to be executed by Java run time system called JVM. • Once run time package is available any java program can run on it. • If program compiled to its native code, different versions of same program will be available.

  10. CDN Diagram

  11. CDN • CDN is Content Distributed Network • CDN is a collection of proxies that acts as intermediaries between the origin server & end client. • Uses bloom filters (Boolean lookup function) to store approximate state of object. • Bloom filter uses hash functions.

  12. Store Proxy • It consists of file that stores all objects & data about objects. • Each object is stored as an array of byte in file. • Offset of this array in the file determines the object’s Persistent IDentifier(PID) • Disadvantage is lack of garbage collection & fragmentation.

  13. Conclusion • “Maintaining the accurate state for objects accessed by a large fraction of the request and approximate state for the remaining objects consuming much of space yields large memory savings and reduced errors (5-10 % of errors). “

  14. Bibliography [1] Purushottam Kulkarni, Prashant Shenoy and Weibo Gong, ” Scalable Techniques for Memory–efficient CDN Simulations ”, Computer Science Dept & ECE Department University of Massachusetts, Amherst MA 01003.

  15. Question & Answer

  16. Thank You..

More Related