The ROOT TTree data format encodes hundreds of petabytes of High Energy and Nuclear Physics events. Its columnar layout drives rapid analyses, as only those parts ("branches") that are really used in a given analysis need to be read from storage. Its unique feature is the seamless C++ integration, which allows users to directly store their event classes without explicitly defining data schemas. In this contribution, we present the status and plans of the future ROOT 7 event I/O. Along with the ROOT 7 interface modernization, we aim for robust, where possible compile-time safe C++ interfaces to read and write event data. On the performance side, we show first benchmarks using ROOT's new experimental I/O subsystem that combines the best of TTrees with recent advances in columnar data formats. A core ingredient is a strong separation of the high-level logical data layout (C++ classes) from the low-level physical data layout (storage backed nested vectors of simple types). We show how the new, optimized physical data layout speeds up serialization and deserialization and facilitates parallel, vectorized and bulk operations. This lets ROOT I/O run optimally on the upcoming ultra-fast NVRAM storage devices, as well as file-less storage systems such as object stores.

中文翻译：

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ROOT 树 I/O 的演变

ROOT TTree 数据格式编码数百 PB 的高能和核物理事件。它的柱状布局推动了快速分析，因为只有在给定分析中真正使用的那些部分（“分支”）才需要从存储中读取。它的独特之处在于无缝的 C++ 集成，它允许用户直接存储他们的事件类，而无需明确定义数据模式。在这篇文章中，我们介绍了未来 ROOT 7 事件 I/O 的状态和计划。随着 ROOT 7 接口的现代化，我们的目标是实现健壮的、编译时安全的 C++ 接口来读取和写入事件数据。在性能方面，我们展示了使用 ROOT 新的实验性 I/O 子系统的第一个基准测试，该子系统结合了 TTrees 的优点和列数据格式的最新进展。核心要素是高级逻辑数据布局（C++ 类）与低级物理数据布局（存储支持的简单类型嵌套向量）的强分离。我们展示了新的、优化的物理数据布局如何加速序列化和反序列化，并促进并行、矢量化和批量操作。这让 ROOT I/O 在即将推出的超快速 NVRAM 存储设备以及无文件存储系统（如对象存储）上以最佳方式运行。