EventStore project was designed to replace existing data access model based on Objectivity DB for CLEO-c collaboration. The EventStore handles efficiently and reliably the data coming from CLEO detector. We expect to store around 200TB of data by 2008.

The EventStore developed to work on the following platforms:

• SunOS 2.6 and Solaris 2.8, 9, 10
• Linux, RedHat 9, RedHat Enterprise 3, 4, Scientific Linux

and supports various DB backends:

• SQLite
• MySQL
• we plan to use DB2 or ORACLE at peak of data taking

Short summary:

• support various file formats, including raw (binary) and PDS.
• handle raw, reconstructed and MonteCarlo data
• allow various data access patterns, including MetaData access
• data versioning and reproducability
• reliable and fault tolerant data access (multiple DB servers, interaction with HSM)
• fast data access and readback
• multiple DB backends (SQLite, MySQL), additional plugins can be easily added

For full list, please visit this page.

SQLite DB doesn't support nested transactions. Load balancing for data access is required.

To fullfill our goal we decided to index data and store navigation information for data access into a backend database. The data themselves can reside elsewhere: on tape, disk servers or user desktops/laptops. As shown in figure, a client application suez uses EventStore to provide access to data through various layers. A three major ones are DB, Management and data delivery layer. A separate toolkit has been used to feed EventStore DB. Full implementation was done in C++ for the client code and in Python for administrative toolkit. We achieved a good performance of reading data at the level of 20K events/second on Linux 1GHz/512MB platform. The details of this work has been published in CHEP'04 (PDF ) and DPF'04 (PDF) conference proccedings, slides from my talk at DPF available here.