Expected File Characteristics and Access Patterns

• The raw data arrive time-ordered in bursts every 15 seconds; each burst's data is a single file (size about 100-300 MBytes).
• Files are accessed sequentially (random access within the file is not necessary (or occurs very rarely). No entity smaller than a whole file ist to be managed by the Storage Management System (SMS).
• All files are write-once, delete-never.
• Online Production: Multiple streams of selected, reformatted and/or reconstructed data are produced for later analysis. They have to be managed by the SMS together with the raw-data.
• Test Analysis: This s typically run during data-taking, in parallel with online production. Here, the data access pattern is very different and may be purely random.
• Off-line Production: After data taking a final production is made, accessing all the data gathered during the physics run in time-order.
• Off-line Analysis: Compared to the test analysis, the number of users is greater and longer sequences of consecutive bursts will be read using the results of the off-line production.