A dynamic file replication based on CPU load and consistency mechanism in a trusted distributed environment

Pokušalo se predložiti dinamički, kooperativni, pouzdani i sigurni pristup replikaciji datoteke utemeljen na opterećenosti CPU uz konzistenciju među replikama datoteke za distribuirano okruženje. Rezultati simulacije koja se sastoji od 100 potrebnih čvorova, tri servera datoteke i datoteke veličine od 677 KB to 11 MB pokazuju da kada se uzme u obzir opterećenje CPU, prosječno smanjenje vremena potrebnog za popunjavanje datoteke je oko 22,04 ÷ 24,81 %. Tako se optimiziralo opterećenje CPU i smanjilo traženo vrijeme popunjavanja datoteke. Opterećenje CPU smanjuje se za 4,25 ÷ 5,58 %. Rezultati pokazuju da se prosječno kašnjenje upisa (write latency) s predloženim mehanizmom smanjuje za 6,12 % u usporedbi sa Spinnakerovim, a prosječno vrijeme čekanja čitanja (read latency) je 3 puta bolje od Cassandra Quorum Read (CQR). Predložena parcijalna propagacija ažuriranja za održavanje konzistencije datoteke povećava se do 69,67 % u odnosu na vrijeme potrebno za ažuriranje zastarjelih replika. Tako je integritet datoteka i ponašanje zahtijevanih čvorova i servera datoteke zagarantirano za čak manje vremena. Konačno, kroz algebra postupak uspostavljen je odnos između formalnih aspekata jednostavnog modela sigurnosti i sigurnog pouzdanog modela replikacije datoteke zasnovanog na sigurnom pouzdanom opterećenju datoteke.An effort has been made to propose a CPU load based dynamic, cooperative, trust based, and secure file replication approach based along with consistency among file replicas for distributed environment. Simulation results consisting of 100 requesting nodes, three file servers and file size ranging from 677 KB to 11 MB establishes that, when the CPU load is taken into consideration, the average decrease in file request completion time is about 22,04 ÷ 24,81 % thus optimizing the CPU load and minimizing the file request completion time. The CPU load decreases by 4,25 ÷ 5,58 %. Results show that, the average write latency with proposed mechanism decreases by 6,12 % as compared to Spinnaker writes and the average read latency is 3 times better than Cassandra Quorum Read (CQR). The proposed partial update propagation for maintaining file consistency stands to gain up to 69,67 % in terms of time required to update stale replicas. Thus the integrity of files and behaviour of the requesting nodes and file servers is guaranteed within even lesser time. Finally, a relationship between the formal aspects of simple security model and secure reliable CPU load based file replication model is established through process algebra

Multi-agent based architecture for digital libraries

Digital Libraries (DL) generally contain a collection of independently maintained data sets, in different formats, which may be queried by geographically dispersed users. The general problem of managing such large digital data archives is particularly challenging when the system must cope with data which is processed on demand. This dissertation proposes a Multi-Agent System (MAS) architecture for the utilisation of an active DL that provides computing services in addition to data-retrieval services, so that users can initiate computing jobs on remote supercomputers for processing, mining, and filtering of the data in the library. The system architecture is based on a collaborative set of agents, where each agent undertakes a pre-defined role, and is responsible for offering a particular type of service. The integration of services is based on a user defined query which can range in complexity from simple queries, to specialised algorithms which are transmitted to image processing archives as mobile agents. The proposed architecture enables new information sources and services to be integrated into the system dynamically, supports autonomous and dynamic on-demand data processing based on collaboration between agents, capable of handling a large number of concurrent users. Focus is based on the management of mobile agents which roam through the servers that constitute the DL to serve user queries. A new load balancing scheme is proposed for managing agent load among the available servers, based on the system state information and predictions about lifetime of agent tasks and server status. The system architecture is further extended by defining a gateway to provide interoperability with other heterogeneous agent-based systems. Interoperability in this sense enables agents from different types of platforms to communicate between themselves and use services provided by other systems. The novelty of the proposed gateway approach lies in the ability to adapt an existing legacy system for use with the agent-based approach (and one that adheres to FIPA standards). A prototype has been developed as a proof-of-concept to outline the principles and ideas involved, with reference to the Synthetic Aperture Radar Atlas (SARA) DL composed of multi-spectral remote-sensing imagery of the Earth. Although, the work presented in this dissertation has been evaluated in the context of SARA DL, the proposed techniques suggest useful guidelines that may be employed by other active archival systems