Objectivity/Corba distributed database performance on a gigabit Sun-Ultra-10 cluster

Dynacore's project objective is to provide tools for the remote operation o f large physics experiments [1], [2], [3]. Our group concentrates on the de sign of a remote control room for the Textor-94 plasma-physics experiment [ 4], which will incorporate a distributed database, accessible with Corba ov er Internet [5]. During normal operation, Textor-94 generates hundreds of m egabytes of measurement data within the few seconds of a plasma shot. These shots are generated approximately every ten minutes, in total around 30 sh ots per day. A database will make the measurement data available to scienti sts, both at the experiment and in remote control rooms, which can be locat ed in different countries, within minutes after the acquisition. Fast acces s to the database and a high data-storage speed are, therefore, of utmost i mportance. We have defined a set of data objects, which allow storage of virtually any kind of Terror measurement data. An Objectivity [6] object-oriented databa se is used to store these objects. We have also designed an architecture in which database clients access the measurement database solely via data man agers with Corba-interfaces. The data managers introduce security into the database, and also hide details of the database implementation for the user s. An object manager provides clients with a central starting point, and di stributes the total database load in an intelligent way over all available data-managers. We have tested the performance of our architecture on a computer cluster co nsisting of eight Sun-Ultra-10 workstations [7]. These computers are interc onnected with 1-gigabit/s Ethernet fiber-optic links over two Cabletron SSR -8000 IP routers, and also via 100 Mbit/s Ethernet UTP cables over one Cabl etron SS-6000 [8]. This article will discuss the database model, the distri buted architecture and the performance measurements results. The measuremen ts showed that our high performance goals can be achieved with the presente d architecture.