EggsFS

A distributed file system. No high level description yet apart from a somewhat outdated proposal. If you have questions you're probably better off asking @fmazzol.

EggsFS is a collection of binaries starting with eggs, plus a kernel module, eggsfs.ko. Specifically:

• eggsshard and eggscdc, are the processes storing the metadata (what directories and files are on the filesystem);
• eggsblocks reads and writes blobs of data (blocks), of which files are made of;
• eggsshuckle acts a nameserver of sorts storing where the shards, CDC, and block services are;
• eggsgc continuously scans the filesystem for garbage that can be collected;
• eggscli is a command line tool to interact with the filesystem directly, and also perform some maintenance tasks (e.g. migrating the contents of a block service);
• eggsfuse is an EggsFS client implemented with fuse;
• eggsfs.ko is an EggsFS client implemented as a kernel module;
• eggsrun is a tool to quickly spin up an EggsFS instance;
• eggstests runs some integration tests.

eggsshard and eggscdc are written in C++. eggsfs.ko is written in C (duh). Everything else is written in Go.

Building

% ./build.sh alpine

Will build all the artifacts apart from the Kernel module. The output will be in build/alpine. Things will be built in an Alpine Linux container, so that everything will be fully statically linked. ./build.sh release will build outside the container, everything will still be linked statically apart from glibc, which cannot be reliably linked statically.

Playing with a local EggsFS instance

% cd go/eggsrun
% go run . -dir <data-dir>

The above will run all the processes needed to run EggsFS. This includes:

• 256 metadata shards;
• 1 cross directory coordinator (CDC)
• A bunch of block services (this is tunable with the -flash-block-services, -hdd-block-services, and -failure-domains flags)
• 1 shuckle instance

A multitude of directories to persist the whole thing will appear in <data-dir>. The filesystem will also be mounted using FUSE under <data-dir>/fuse/mnt.

Building the Kernel module

% cd kmod
% ./fetchlinux.sh # fetch linux sources
% (cd linux && make oldconfig && make prepare && make -j) # build Linux
% make KDIR=linux -j kmod

Playing with the Kernel module

There's infrastructure to spin up a minimal QEMU image with eggsfs.ko inserted, see kmod/restartsession.sh.