Virtualization Technique For Replica Synchronization

Transcription

1 Virtualization Technique For Replica Synchronization By : Ashwin G.Sancheti ashwin@cs.jhu.edu Instructor : Prof.Randal Burns Date : 19 th Feb 2008

2 Roadmap Motivation/Goals What is Virtualization? Advantages? My Previous work Architecture and design Algorithm and working Pros and cons for my work New proposed idea Different approaches for the same Conclusion

3 Problem and Motivation Redundancy in Replica Synchronization To transfer the redundant information which might already present the receiver side. Time required to transfer the data is very high. Disk space usage More I/O e.g.: Patch update example

4 Goal To extract the common part (Delta) part between two virtual machine and transfer only the common part with minimum transmission delay. Reduce the I/O traffic Reduce the disk space

5 Two Solutions: TAPER Algorithm Replayfs trace (VFS approach)

6 Non virtual machine and VM

7 Advantages Server Consolidation Testing and development Dynamic Load Balancing Disaster Recovery Resource sharing Reduce power consumption Reduce the land requirement Many others

8 My Work Current Problem : Large Disk Space to store multiple virtual machines. Goal : To get the delta part between two virtual machines and delete one virtual machine. Save lots of space. Example : Windows 2K Server (Plain Vanilla) Windows 2K + Exchange Server

9 Architecture and Design VMDK Architecture Sparse header Descriptor table Grain Directories Grain tables Grain Size CRC computation Algorithm to compute the delta part

10 Test cases and Results VM 1 : Win 2000 (Plain) Size :1 GB VM 2 : Win Exchange Server VM 2 : Win Exchange Server Size : 1.3 GB Delta VM: Only Exchange Server Size : 120 MB

11 New proposal Goal : To get the Delta/Common part between the client machine and the remote machine with minimum transmission delay. Advantages No need to transmit whole virtual machine. Less time to transmit the data.

12 First Approach TAPER Algorithm Directory tree synchronization protocol between source and target node Works in four phases Directory tree Large chunks Smaller blocks Bytes

13 First Approach(Conti..) Directory Matching Eliminates identical portions of the directory tree that are common in content and structure Hierarchical hash tree implementation

14 First Approach(Conti ) Matching Chunks Now we are left with unmatched files at the source and Target. Use content-defined chunking (CDC) to reduce the unmatched data. Boundary for chunk is defined by Rabin Fingerprinting (?) Target send the SHA values for all the remaining files to the source

15 First Approach(Conti ) Matching Blocks Each file at the source will be series of matched and unmatched regions (holes) Fine grained block matching is performed so we Fine grained block matching is performed so we will left with unmatched data blocks at source side. Matching Bytes The blocks in the unmatched data are delta encoded with similar blocks in matched set. Finally remaining unmatched data and delta bytes are sent to the target using standard compression algorithm.

16 Second Approach Perform the comparison at the VFS level. Replayfs : Replaying file system traces at the VFS level. Main goal : To reproduce the original file system workload as accurately as possible

17 Replayfs Component Raw traces and re-playable traces Trace compiler : To get the raw traces Command Sequence of VFS operations with their associated timestamps, process ID Actual return value is compared with the return value captured in the original trace.

18 Replayfs (Conti ) Resource Allocation Table (RAT) To refer to the command parameters and the return values. Always kept in the memory.

19 Replayfs(Conti ) Memory buffers Largest component of the Replayfs trace Necessary to replay the trace. Includes file name and buffers to be written in future.

20 Conclusion Detecting common part between two virtual machine reduces the disk space drastically. TAPER is one of the algorithm to get the common part. Another approach we can choose as capturing traces at VFS level(replayfs)

21 References TAPER: Tiered Approach for Eliminating Redundancy in Replica Synchronization University of Texas Austin Accurate and Efficient Replaying of File System Traces Stony Brook University

22 THANK YOU Any questions?