backing_up_data.rst

title:	Backing up Data
description:	Backing up stateful data on Deis.

Backing up Data

While applications deployed on Deis follow the Twelve-Factor methodology and are thus stateless, Deis maintains platform state in two places: the :ref:`Store` component, and in etcd.

Store component

The store component runs Ceph, and is used by the :ref:`Database` and :ref:`Registry` components as a data store. This enables the components themselves to freely move around the cluster while their state is backed by store.

The store component is configured to still operate in a degraded state, and will automatically recover should a host fail and then rejoin the cluster. Total data loss of Ceph is only possible if all of the store containers are removed. However, backup of Ceph is fairly straightforward.

Data in Ceph is stored on the filesystem in /var/lib/ceph, and metadata information is stored within Ceph. Ceph provides the ability to take snapshots of storage pools with the rados command.

Using pg_dump

Since the database component runs PostgreSQL, pg_dumpall can also be used to generate a text dump of the database.

dev $ fleetctl ssh deis-database.service
coreos $ nse deis-database
coreos $ sudo -u postgres pg_dumpall > pg_dump.sql

etcd

Service state and fleet scheduling data is stored in etcd. Unfortunately, there is currently no recommended backup solution for etcd. However, there is a third-party tool called etcd-dump which can be used to dump the data stored in etcd.

Official backup recommendations for etcd are forthcoming. The CoreOS team is tracking etcd update documentation in #683.