chainfs

README

ChainFS Graph Driver

EXPERIMENTAL!

Note that this is still in development and experimental.

About

The chainfs graph driver leverages libchainfs (https://github.com/libopenstorage/chainfs) user space layered filesystem to create a storage of graph layers.

libchainfs can we configured to use an object store interface to read, write and create snapshots. The provider of this interface is passed in via the chainfs.volume_driver parameter when starting Docker.

It also uses an optimized way of computing the layer diffs and avoids using the NaiveDiff implementation.

To use this as the graphdriver in Docker with btrfs as the backend volume provider:

DOCKER_STORAGE_OPTIONS= -s chainfs --storage-opt chainfs.volume_driver=btrfs

or

docker daemon --storage-driver=chainfs --storage-opt chainfs.volume_driver=btrfs

Note that the chainfs.volume_driver parameter will indicate the actual volume provider to be used by chainfs. chainfs exposes a set of interfaces that will be called by libchainfs to perform the create, read, write, truncate object store operations.

Building

Installing Dependancies

1. Make sure you have fuse installed.
2. Make sure you have libchainfs installed. Visit https://github.com/libopenstorage/chainfs to obtain libchainfs.

To build OSD

When building OSD, run:

HAVE_CHAINFS=1 EXPERIMENTAL_=1 make

Running

Here is a sample config.yaml file to load the chainfs graph driver:

---
osd:
  cluster:
     nodeid: "1"
     clusterid: "deadbeeef"
  drivers:
     btrfs:
  graphdrivers:
     chainfs:

Note

Set your ulimit -n to run out of open files. Graph drivers tend to have many concurrently open files.

Documentation

Index

• Constants
• func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error)

Constants

const (
	// Name of the driver
	Name = "chainfs"
	// Type of the driver
	Type = api.DriverType_DRIVER_TYPE_GRAPH
)

Functions

func Init

func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error)

Init initializes the graphdriver