Sheepfs

Vasiliy Tolstov edited this page Aug 7, 2015 · 9 revisions

Introduction

Sheepfs is a FUSE-based pseudo file system in userland to access both sheepdog's internal state (for e.g, cluster info, vdi list) as well as sheepdog's high reliable storage.

The idea here is that its sometimes useful that we can envision our interaction with an sheepdog's object in terms of a directory structure and filesystem operations.

People might be mostly interested into sheepfs's volume directory, which export VM's volume as a pseudo block file in your local file system hierarchy, which can be used as

  1. a big file abstraction, which is actually backed by Sheepdog's storage, distributed in the cluster.
  2. a loop device file, which you can mount wherever you want to use it as a file system backed up by Sheepdog.
  3. a loop device file for some VM's image, which you want to access(RW) its internal data.
  4. storage media for other hypervisor, such as XEN

This file abstraction integrates well into kernel's pagecache.

Enable sheepfs

To compile sheepfs, you need install FUSE devel files.

$ sudo apt-get install libfuse-dev

Then sheepfs will be automatically compiled in. The binary will be located in sheepfs/sheepfs.

Example

Some example to show how we can use it. sheepfs -h for more help.

$ sheepfs /your/mountpoint

The mountpoint is where we mount our sheepfs, you need to mkdir it first on your own.

To get cluster info:

$ cat sheepfs_dir/cluster/info
Cluster status: running

Cluster created at Mon May 14 15:45:37 2012

Epoch Time           Version
2012-05-14 15:45:38      1 [127.0.0.1:7000, 127.0.0.1:7001, 127.0.0.1:7002]

To attach the the volume named of 'test' (that needs to be already created):

$ echo test > sheepfs_dir/vdi/mount

Then it will show up at sheepfs_dir/volume/test as a normal file which you can read/write in whatever way you want.

We can boot it if it is a bootable image:

$ qemu-system-x86_64 --enable-kvm -m 1024 -drive file=sheepfs_dir/volume/test,cache=writeback.

Or we can even format it as a file system and mount it somewhere to host our data:

$ mkfs.ext4 sheepfs_dir/volume/test
$ sudo mount -o loop sheepfs_dir/volume/test /somewhere

To attach to a snapshot 'mysnap' of a volume named 'test':

$ dog vdi clone -s 'mysnap' test testclone
$ echo testclone > sheepfs_dir/vdi/mount

Proceed as above for a normal vdi.

When the connected sheep daemon crashes, we can re-connect to another live sheep deamon on the fly:

$ echo ip:port > sheepfs_dir/config/sheep_info

When you are done with sheepfs, you can umount the sheepfs directory

$ umount sheepfs_dir

Sheepfs for HTTP storage

We can also use sheepfs to access objects in HTTP storage.

First set address of sheep daemon:

$ sheepfs /your/mountpoint
$ echo "server_ip:server_port" > /your/mountpoint/http/address

Then we can echo full path of object (if we have account "robin", container "fruit", object "one"):

$ echo "/robin/fruit/one" > /your/mountpoint/http/object

Then we can see a file as "/your/mountpoint/http/robin/fruit/one"

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