Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from send...Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from sending WORKDONE/PREPARED message and restrict them from lending data so that transaction abort chain is limited to one. Thus, transaction execution time increases. This paper proposes a modified real time commit protocol for distributed real time database systems (DRTDBS), Allow Commit Dependent and in Time borrowers for Incredible Value added data lending without extended abort chain (ACTIVE), where borrower cohorts are categorized as commit and abort dependent. Further, the commit dependent borrowers can lend data to executing cohorts with still limiting the transaction abort chain to one only and reducing the data inaccessibility. Also, an incoming executing cohort having borrowing factor greater than one can only borrow the dirty data items from lender. This minimizes the fruitless borrowing by the cohort. The performance of ACTIVE is compared with PROMPT, 2SC and SWIFT protocols for both main memory resident and disk resident databases with and without communication delay. Simulation results show that the proposed protocol improves the system performance up to 4% as transaction miss percentage.展开更多
Distributed metadata consistency is one of the critical issues of metadata clusters in distributed file systems. Existing methods to maintain metadata consistency generally need several log forced write operations. Si...Distributed metadata consistency is one of the critical issues of metadata clusters in distributed file systems. Existing methods to maintain metadata consistency generally need several log forced write operations. Since synchronous disk IO is very inefficient, the average response time of metadata operations is greatly increased. In this paper, an asynchronous atomic commit protocol （ACP） named Dual-Log （DL） is presented. It does not need any log forced write operations. Optimizing for distributed metadata operations involving only two metadata servers, DL mutually records the redo log in counterpart metadata servers by transferring through the low latency network. A crashed metadata server can redo the metadata operation with the redundant redo log. Since the latency of the network is much lower than the latency of disk IO, DL can improve the performance of distributed metadata service significantly. The prototype of DL is implemented based on local journal. The performance is tested by comparing with two widely used protocols, EP and S2PC-MP, and the results show that the average response time of distributed metadata operations is reduced by about 40%-60%, and the recovery time is only I second under 10 thousands uncompleted distributed metadata operations.展开更多
为有效地保证分布式事务的ACID性质以及解决多个客户程序并发访问某一事务所造成的访问冲突,根据CORBA对象事务服务OTS(Object Transaction Service)、并发控制服务CCS(Concurrency Control Service)及其提供的相关接口,采用两步提交协...为有效地保证分布式事务的ACID性质以及解决多个客户程序并发访问某一事务所造成的访问冲突,根据CORBA对象事务服务OTS(Object Transaction Service)、并发控制服务CCS(Concurrency Control Service)及其提供的相关接口,采用两步提交协议和并发控制锁机制实现。并将两者相结合实现一个账户之间的转账操作,证明其可行性。展开更多
文摘Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from sending WORKDONE/PREPARED message and restrict them from lending data so that transaction abort chain is limited to one. Thus, transaction execution time increases. This paper proposes a modified real time commit protocol for distributed real time database systems (DRTDBS), Allow Commit Dependent and in Time borrowers for Incredible Value added data lending without extended abort chain (ACTIVE), where borrower cohorts are categorized as commit and abort dependent. Further, the commit dependent borrowers can lend data to executing cohorts with still limiting the transaction abort chain to one only and reducing the data inaccessibility. Also, an incoming executing cohort having borrowing factor greater than one can only borrow the dirty data items from lender. This minimizes the fruitless borrowing by the cohort. The performance of ACTIVE is compared with PROMPT, 2SC and SWIFT protocols for both main memory resident and disk resident databases with and without communication delay. Simulation results show that the proposed protocol improves the system performance up to 4% as transaction miss percentage.
基金supported by the National Basic Research 973 Program of China under Grant No.2011CB302304the NationalHigh Technology Research and Development 863 Program of China under Grant Nos.2011AA01A102 and 2013AA013205+1 种基金the StrategicPriority Research Program of the Chinese Academy of Sciences under Grant No.XDA06010401the Chinese Academy of SciencesKey Deployment Project under Grant No.KGZD-EW-103-5(7)
文摘Distributed metadata consistency is one of the critical issues of metadata clusters in distributed file systems. Existing methods to maintain metadata consistency generally need several log forced write operations. Since synchronous disk IO is very inefficient, the average response time of metadata operations is greatly increased. In this paper, an asynchronous atomic commit protocol （ACP） named Dual-Log （DL） is presented. It does not need any log forced write operations. Optimizing for distributed metadata operations involving only two metadata servers, DL mutually records the redo log in counterpart metadata servers by transferring through the low latency network. A crashed metadata server can redo the metadata operation with the redundant redo log. Since the latency of the network is much lower than the latency of disk IO, DL can improve the performance of distributed metadata service significantly. The prototype of DL is implemented based on local journal. The performance is tested by comparing with two widely used protocols, EP and S2PC-MP, and the results show that the average response time of distributed metadata operations is reduced by about 40%-60%, and the recovery time is only I second under 10 thousands uncompleted distributed metadata operations.
文摘为有效地保证分布式事务的ACID性质以及解决多个客户程序并发访问某一事务所造成的访问冲突,根据CORBA对象事务服务OTS(Object Transaction Service)、并发控制服务CCS(Concurrency Control Service)及其提供的相关接口,采用两步提交协议和并发控制锁机制实现。并将两者相结合实现一个账户之间的转账操作,证明其可行性。
