Crimson

Project Crimson is a prototype to demonstrate available performance in a design that can be extended to support the requirements of a Ceph OSD.

Introduction

Our goals are to optimize the 'top half' of the Ceph OSD, providing a single fast path from network to memory. Using this, we can then reason effectively about the performance of other design decisions, such as Newstore, DM-Clock, and replication and consistency tradeoffs.

Development

For our first, basic prototype, we shall:

• Base our design on the Seastar framework
• Include a high performance memory backend
• Use Cap'n Proto/Flatbuffers style messaging (we aren't committing to any library, this refers to a family of serialziation formats that are low overhead and work well with RDMA.)
• Support both Placement Group and Flexible Placement systems
• We shall not implement snapshots or replication in this pass. Instead we shall include the placement group total ordering, and add null functions for both. (For reasoning about performance we could configure these to have specific time costs to simulate them, and help us figure out where best and how to insert them.)

Building

You will need

• cmake

• Seastar
  it may be fetched with

    git clone git://github.com/scylladb/seastar.git
  

  and built with

    ./configure.py
    ninja-build
  

  For more info read Seastar's install instructions.

This project uses git submodules. Before building, make sure to execute

git submodule update --init --recursive

Call CMake and build make. If you have seastar installed in a nonstandard location, use a line like

PKG_CONFIG_PATH=/path/to/seastar/build/release cmake /path/to/crimson

(Substitute debug for release if you wish.)

Future

Currently this is a prototype and tool to reason about performance. if it proves useful it may have compatibility with Ceph wire protocol added and grow into a high performance 'new OSD'.