ROOT I/O improvements for HEP analysis

We overview recent changes in the ROOT I/O system, increasing performance and enhancing it and improving its interaction with other data analysis ecosystems. Both the newly introduced compression algorithms, the much faster Bulk I/O data path, and a few additional techniques have the potential to significantly to improve experiments' software performance. The need for efficient lossless data compression has grown significantly as the amount of HEP data collected, transmitted, and stored has dramatically increased during the LHC era. While compression reduces storage space and, potentially, I/O bandwidth usage, it should not be applied blindly: there are significant trade-offs between the increased CPU cost for reading and writing files and the reduce storage space. As ROOT I/O is responsible for providing serializing functionality for complex C++ objects, for example for physics reconstruction. At the same time, analysis workflows typically have simpler objects compared to reconstruction. This later case's performance can be improve by using the ROOT "bulk I/O" interface, allowing to access multiple events to be returned per one library call