1. Performance-sensitive Service Provision in Active Digital Libraries Georgousopoulos Christos Omer F. Rana http://www.cs.cf.ac.uk/Digital-Library/

2. Load balance mobilestatic statemodel Market mechanism Specialized agents gather System state information Aim: improve the average utilization and performance of tasks on available servers Kinds of Load Balance (LB): Keren & Barak: mobile LB has a 30-40% improvement over the static placement scheme only a price sophistiated auction protocols a pricing mechanism without any negotiation roam through the network bid for resources L OAD B ALANCING O VERVIEW +

3. A RCHITECTURE O F S ARA D IGITAL L IBRARY

4. i) agents’ tasks ii) servers’ utilization (performance load) iii) availability of resources iv) network efficiency  LB decisions are supported through the MAs based on a model which accepts as: input: an agent’s requirements & System state information output: the appropriate server where an agent should migrate to  The model is a function of: Agent tasks may be either simplecomplex simple or complex

5. E XPERMIMENTAL T ESTS O N S ARA L B S CHEME ( U TILISATION O F I NFORMATION- S ERVERS ) Details of experiments conducted: - 200 agents launched - 5 information-servers & 1 web-server (Sun-Ultra 5 workstation running on Solaris 8 with Voyager 4.5 as the agent platform) - 100Mbits/s network connection - data-repository maintained by Oracle 9 DBMS on the execution of agents with mixed tasks (15% where complex task) on the execution of agents with simple tasks

6. For other systems utilising active-archives in which the lifetime of complex tasks cannot be estimated or tend to be erroneous E XPERMIMENTAL T ESTS O N S ARA L B S CHEME ( A DAPTABILITY O F M ODEL ) Three different LB schemes: Scheme No.1 - Scheme No.1 : represents the default LB scheme adopted in SARA MAS (lifetime of complex agent tasks is known) adaptability algorithm Scheme No.2 - Scheme No.2 : alternative version of No.1 (lifetime of complex agent tasks is unknown and therefore not used in calculations) Scheme No.3 - Scheme No.3 : alternative version of No.2 (adaptable algorithm is utilised for amending the server’s utilisation)

7. Optimization of LB scheme No.2, based on the utilisation of the adaptability algorithm Efficiency between LB scheme No.2 & No.3 Total task time required by agents to complete their task optimization in performance 1.63 – 10.8 % E XPERMIMENTAL T ESTS O N S ARA L B S CHEME ( C OMPARISON O N D IFFERENT L B S CHEMES )

8. T h e e n d http://www.cs.cf.ac.uk/Digital-Library/ Performance-sensitive Service Provision in Active Digital Libraries Georgousopoulos Christos Omer F. Rana