Arthur Kreymer - 8 December 1995

E831 Express Analysis System

E831 Express Overview

In the 1990/1992 E687 data run, the ability to analyze small samples of data quickly in the counting room played a major role in our ability to keep the quality of the data high. We also derived some advantage from the "expressline" Silicon Graphics system in the Feynman Center, used to run the occasional full data tape to check charm signals, and used to reconstruct some special calibration runs shortly after they were taken.

For the 1996 E831 data run we are purchasing a dedicated Express Analysis system for counting room. The system will have about 600 SPEC92 of CPU power. The system will be configured with appropriate disk and tape, for software develpment and data handling.

We plan a data taking rate of about 20,000 events per spill, at about 5 KBytes per event. This implies a sustained data rate of about 1.5 MBytes/second and 333 events/second. The full analysis of an average E687 event requires about 20 SPEC-seconds. If everything remains the same for E831, a 500 SPEC farm could analyze 7% of the data.

Event sizes may increase due to the new Vertex and Straw detectors, and analysis time may increase somewhat. But full calorimeter reconstruction will probably not be available, nor will it be necessary for most of the Express monitoring. Streamlined calorimitry will probably bring Express reconstruction time down to half the full E687 reconstruction time, allowing 15% of the events to be analyzed.

A combination of online and offline information will be used to select events with charm content, or special monitoring value. The Express system will write output tapes in DST format, to keep down the tape and data handling costs. We will write no more than a tenth as many tapes as the full data stream.

E831 Express Requirements:

Implementation

Input and output data files will be stored on disk in the Express system. This decouples Express processing from any tape handling problems. Each input file will be analyzed by a single process.

A single Express Host system will receive data from the Data Logger via FDDI or Fast Ethernet. Input data will be stored on three of the Host's 9 GB disks. Output from the EXPRESS analysis processed will be written to two 9 GB disks before spooling to tape.

This is a relatively small system, to be supported with existing resources. We require a hardware and software environment already supported at Fermilab.

Selection

We have purchased Digital Alpha based workstations, based on a competitive bid between Digital, IBM, SGI and SUN. The selection was made based strictly on the performance/price ratio. The specific configuration purchased was chosen based on price, performance, compatibility, networking options, and supportability.

The base system is listed here. We are purchasing additional components (disks, tapes, etc).