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Overview
========
Ceph is a distributed storage and network file system designed to provide
excellent performance, reliability, and scalability.
This charm deploys a Ceph cluster.
Usage
=====
The ceph charm has two pieces of mandatory configuration for which no defaults
are provided:
fsid:
uuid specific to a ceph cluster used to ensure that different
clusters don't get mixed up - use `uuid` to generate one.
monitor-secret:
a ceph generated key used by the daemons that manage to cluster
to control security. You can use the ceph-authtool command to
generate one:
ceph-authtool /dev/stdout --name=mon. --gen-key
These two pieces of configuration must NOT be changed post bootstrap; attempting
to do this will cause a reconfiguration error and new service units will not join
the existing ceph cluster.
The charm also supports the specification of storage devices to be used in the
ceph cluster.
osd-devices:
A list of devices that the charm will attempt to detect, initialise and
activate as ceph storage.
This can be a superset of the actual storage devices presented to each
service unit and can be changed post ceph bootstrap using `juju set`.
The full path of each device must be provided, e.g. /dev/vdb.
For Ceph >= 0.56.6 (Raring or the Grizzly Cloud Archive) use of
directories instead of devices is also supported.
At a minimum you must provide a juju config file during initial deployment
with the fsid and monitor-secret options (contents of cepy.yaml below):
ceph:
fsid: ecbb8960-0e21-11e2-b495-83a88f44db01
monitor-secret: AQD1P2xQiKglDhAA4NGUF5j38Mhq56qwz+45wg==
osd-devices: /dev/vdb /dev/vdc /dev/vdd /dev/vde
Specifying the osd-devices to use is also a good idea.
Boot things up by using:
juju deploy -n 3 --config ceph.yaml ceph
By default the ceph cluster will not bootstrap until 3 service units have been
deployed and started; this is to ensure that a quorum is achieved prior to adding
storage devices.
Contact Information
===================
Author: Paul Collins <paul.collins@canonical.com>,
James Page <james.page@ubuntu.com>
Report bugs at: http://bugs.launchpad.net/charms/+source/ceph/+filebug
Location: http://jujucharms.com/charms/ceph
Technical Bootnotes
===================
This charm uses the new-style Ceph deployment as reverse-engineered from the
Chef cookbook at https://github.com/ceph/ceph-cookbooks, although we selected
a different strategy to form the monitor cluster. Since we don't know the
names *or* addresses of the machines in advance, we use the _relation-joined_
hook to wait for all three nodes to come up, and then write their addresses
to ceph.conf in the "mon host" parameter. After we initialize the monitor
cluster a quorum forms quickly, and OSD bringup proceeds.
The osds use so-called "OSD hotplugging". **ceph-disk-prepare** is used to
create the filesystems with a special GPT partition type. *udev* is set up
to mount such filesystems and start the osd daemons as their storage becomes
visible to the system (or after "udevadm trigger").
The Chef cookbook mentioned above performs some extra steps to generate an OSD
bootstrapping key and propagate it to the other nodes in the cluster. Since
all OSDs run on nodes that also run mon, we don't need this and did not
implement it.
See http://ceph.com/docs/master/dev/mon-bootstrap/ for more information on Ceph
monitor cluster deployment strategies and pitfalls.
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