ROOT provides an flexible format used throughout the HEP community. The
number of use cases - from an archival data format to end-stage analysis - has
required a number of tradeoffs to be exposed to the user. For example, a high
"compression level" in the traditional DEFLATE algorithm will result in a
smaller file (saving disk space) at the cost of slower decompression (costing
CPU time when read). At the scale of the LHC experiment, poor design choices
can result in terabytes of wasted space or wasted CPU time. We explore and
attempt to quantify some of these tradeoffs. Specifically, we explore: the use
of alternate compressing algorithms to optimize for read performance; an
alternate method of compressing individual events to allow efficient random
access; and a new approach to whole-file compression. Quantitative results are
given, as well as guidance on how to make compression decisions for different
use cases.Comment: Proceedings for 22nd International Conference on Computing in High
Energy and Nuclear Physics (CHEP 2016
