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http://hpds.ee.kuas.edu.tw/. dRamDisk: Efficient RAM Sharing on a Commodity Cluster. Vassil Roussev, Golden G. Richard. Reporter : Min-Jyun Chen. publication year :2006. Abstract.

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  1. http://hpds.ee.kuas.edu.tw/ dRamDisk: Efficient RAM Sharing on a Commodity Cluster Vassil Roussev, Golden G. Richard Reporter : Min-Jyun Chen publication year :2006

  2. Abstract The main point of the paper is to present a practical solution—a distributed RAM disk (dRamDisk) with an adaptive read-ahead scheme—which demonstrates that spare RAM capacity can greatly benefit I/O-constrained applications. Our experiments show that sequential read/write operations can be sped up approximately 3.5 times relative to a commodity hard drive. KUAS-EE-HPDS

  3. Contents 1. Introduction 2.Design rationale 3.Implementation issues 4. Evaluation 5. Conclusion

  4. Introduction • Better performance—using remote RAM should yield non-trivial performance gains. • Transparency—RAM sharing should be transparent to the process. • Efficiency—this requirement has two sides: • The system should utilize as much as possible of the available network resources. • A CPU-bound process should see no performance degradation. • Ease of use—the systems should be easy to deploy and administer. KUAS-EE-HPDS

  5. Design rationale The dRamDisk Architecture- KUAS-EE-HPDS

  6. Design rationale (Cont.) User-level RAM server - One obvious drawback is that allocated memory cannot be locked into RAM so there is the potential for it to be swapped out by the paging system. Our rationale is that, for an idle system, the issue is moot—the user process will be able to use up all available memory simply because there is no competition. KUAS-EE-HPDS

  7. Design rationale (Cont.) Block-level device driver- • There are two obvious choices here. • The first one is to implement file system-level caching, which would allow optimizationsbased on the logical structure of the file system (FS). • The alternative is to implement a (block-level) device that does not have the benefit of filesystem knowledge but would work with any filesystem. KUAS-EE-HPDS

  8. Design rationale (Cont.) TCP-based communication- IT users have been very reluctant to adopt more efficient solutions designed to take advantage of more efficient communication technologies . As a result, many vendors are providing TCP/IP emulation that enables users to take advantage of the optimization without parting with the “good old” TCP/IP sockets. KUAS-EE-HPDS

  9. Implementation issues • We implemented an adaptive read-ahead scheme to accommodate the conflicting requirements of small and large files: • The initial transfer unit is set to the minimum (4KB). • If a successive block request is adjacent to the previous block transferred, the size of the transfer unit is doubled subject to a maximum parameter (128KB). • Otherwise, the transfer unit is set to the minimum. KUAS-EE-HPDS

  10. Evaluation Experimental setup- 5 x Dell Pentium 4 @ 3GHz/2GB RAM 1 x Gigabit 8-port Linksys Workgroup Switch Linux 2.4 kernel One host was dedicated to running the application/benchmark. Other four host were providing the distributed block device (i.e., all I/O requests/results cross the network). KUAS-EE-HPDS

  11. Evaluation (Cont.) Benchmark results- For our benchmark testing, we used the IOzone file system benchmark tool (http://www.iozone.org) . And ran identical tests for both the local and the network drives. KUAS-EE-HPDS

  12. Evaluation (Cont.) Benchmark results- KUAS-EE-HPDS

  13. Evaluation (Cont.) Application results- • We used three different command-line tools: • tar—the standard Unix archiving utility. • md5sum—a tool for computing MD5 file hashes. • scalpel—an optimized tool for carving files out of a disk image . KUAS-EE-HPDS

  14. Evaluation (Cont.) Application results- KUAS-EE-HPDS

  15. Conclusions Unlike previous work, our solution is targeted at improving sequential read/write operations,which are the dominant disk access pattern. Our experiments show that sequential read/write operations can be sped up approximately 3.5 times relative to a commodity IDE hard drive. Furthermore, this speedup is approximately 90% of what is practically achievable for the tested system. KUAS-EE-HPDS

  16. Thank You ! http://hpds.ee.kuas.edu.tw/

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