507c190c97
There should be 'OpenStack Administrator Guide' for the title, not 'Administrator Guide'. Change-Id: Ia53fe2c159ea697abd50169966cd7a68f4c18f8d Closes-Bug: #1584810
86 lines
2.7 KiB
ReStructuredText
86 lines
2.7 KiB
ReStructuredText
|
|
.. _storage-ha-backend:
|
|
|
|
================
|
|
Storage back end
|
|
================
|
|
|
|
Most of this guide concerns the control plane of high availability:
|
|
ensuring that services continue to run even if a component fails.
|
|
Ensuring that data is not lost
|
|
is the data plane component of high availability;
|
|
this is discussed here.
|
|
|
|
An OpenStack environment includes multiple data pools for the VMs:
|
|
|
|
- Ephemeral storage is allocated for an instance
|
|
and is deleted when the instance is deleted.
|
|
The Compute service manages ephemeral storage.
|
|
By default, Compute stores ephemeral drives as files
|
|
on local disks on the Compute node
|
|
but Ceph RBD can instead be used
|
|
as the storage back end for ephemeral storage.
|
|
|
|
- Persistent storage exists outside all instances.
|
|
Two types of persistent storage are provided:
|
|
|
|
- Block Storage service (cinder)
|
|
can use LVM or Ceph RBD as the storage back end.
|
|
- Image service (glance)
|
|
can use the Object Storage service (swift)
|
|
or Ceph RBD as the storage back end.
|
|
|
|
For more information about configuring storage back ends for
|
|
the different storage options, see the `OpenStack Administrator Guide
|
|
<http://docs.openstack.org/admin-guide/>`_.
|
|
|
|
This section discusses ways to protect against
|
|
data loss in your OpenStack environment.
|
|
|
|
RAID drives
|
|
-----------
|
|
|
|
Configuring RAID on the hard drives that implement storage
|
|
protects your data against a hard drive failure.
|
|
If, however, the node itself fails, data may be lost.
|
|
In particular, all volumes stored on an LVM node can be lost.
|
|
|
|
Ceph
|
|
----
|
|
|
|
`Ceph RBD <http://ceph.com/>`_
|
|
is an innately high availability storage back end.
|
|
It creates a storage cluster with multiple nodes
|
|
that communicate with each other
|
|
to replicate and redistribute data dynamically.
|
|
A Ceph RBD storage cluster provides
|
|
a single shared set of storage nodes
|
|
that can handle all classes of persistent and ephemeral data
|
|
-- glance, cinder, and nova --
|
|
that are required for OpenStack instances.
|
|
|
|
Ceph RBD provides object replication capabilities
|
|
by storing Block Storage volumes as Ceph RBD objects;
|
|
Ceph RBD ensures that each replica of an object
|
|
is stored on a different node.
|
|
This means that your volumes are protected against
|
|
hard drive and node failures
|
|
or even the failure of the data center itself.
|
|
|
|
When Ceph RBD is used for ephemeral volumes
|
|
as well as block and image storage, it supports
|
|
`live migration
|
|
<http://docs.openstack.org/admin-guide/compute-live-migration-usage.html>`_
|
|
of VMs with ephemeral drives;
|
|
LVM only supports live migration of volume-backed VMs.
|
|
|
|
Remote backup facilities
|
|
------------------------
|
|
|
|
[TODO: Add discussion of remote backup facilities
|
|
as an alternate way to secure ones data.
|
|
Include brief mention of key third-party technologies
|
|
with links to their documentation]
|
|
|
|
|