Note
The Multi Store feature was introduced as EXPERIMENTAL in Rocky and is now fully supported in the Train release.
This page describes how to enable multiple stores in glance.
Glance version 17.0.0 or Later
Glance Store Library 0.25.0 or Later
Glance not using the Glance Registry
Available backends
In this section, we discuss what configuration options are available to operators to enable multiple stores support.
in the [DEFAULT]
options group:
enabled_backends
must be set as a key:value pair where key
represents the identifier for the store and value will be the type
of the store. Valid values are one of file
, http
, rbd
,
swift
, cinder
or vmware
. In order to have multiple stores
operator can specify multiple key:value separated by comma.
Warning
The store identifier prefix os_glance_
is reserved. If you
define a store identifier with this prefix, the glance service will
refuse to start.
The http store type is always treated by Glance as a read-only
store. This is indicated in the response to the /v2/stores/info
call, where an http type store will have the attribute read-only:
True
in addition to the usual id
and description
fields.
[DEFAULT]
enabled_backends = fast:rbd, cheap:rbd, shared:file, reliable:file
in the [glance_store]
options group:
default_backend
must be set to one of the identifier which are defined
using enabled_backends
option. If default_backend
is not set or if
it is not representing one of the valid store drivers then it will prevent
glance api service from starting.
[glance_store]
default_backend = fast
For each of the store identifier defined in enabled_backends
section
operator needs to add a new config group which will define config options
related to that particular store.
[shared]
filesystem_store_datadir = /opt/stack/data/glance/shared_images/
store_description = "Shared filesystem store"
[reliable]
filesystem_store_datadir = /opt/stack/data/glance/reliable
store_description = "Reliable filesystem backend"
[fast]
store_description = "Fast rbd backend"
rbd_store_chunk_size = 8
rbd_store_pool = images
rbd_store_user = admin
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rados_connect_timeout = 0
[cheap]
store_description = "Cheap rbd backend"
rbd_store_chunk_size = 8
rbd_store_pool = images
rbd_store_user = admin
rbd_store_ceph_conf = /etc/ceph/ceph1.conf
rados_connect_timeout = 0
Note
store_description
is a new config option added to each store where
operator can add meaningful description about that store. This
description is displayed in the GET /v2/info/stores response.
Please keep the following points in mind.
Due to the special read only nature and characteristics of the http store type, configuring multiple instances of the http type store is not supported. (This constraint is not currently enforced in the code.)
Each instance of the filesystem store must have a different value
for the filesystem_store_datadir
. (This constraint is not currently
enforced in the code.)
With the Train release, Glance is beginning a transition from its former reliance upon local directories for temporary data storage to the ability to use backend stores accessed via the glance_store library.
In the Train release, the use of backend stores for this purpose is optional unless you are using the multi store support feature. Since you are reading this document, this situation most likely applies to you.
Note
Currently, only the filesystem store type is supported as a Glance reserved store.
The reserved stores are not intended to be exposed to end users. Thus
they will not appear in the response to the store discovery call, GET
/v2/info/stores, or as values in the OpenStack-image-store-ids
response header of the image-create call.
You do not get to select the name of a reserved store; these are defined
by Glance and begin with the prefix os_glance_
. In the Train release,
you do not get to select the store type: all reserved stores must be of
type filesystem.
Currently, there are two reserved stores:
os_glance_tasks_store
This store is used for the tasks engine. It replaces the use of the
DEPRECATED configuration option [task]/work_dir
.
os_glance_staging_store
This store is used for the staging area for the interoperable image
import process. It replaces the use of the DEPRECATED configuration
option [DEFAULT]/node_staging_uri
.
Note
If end user wants to retrieve all the available stores using
CONF.enabled_backeds
then he needs to remove reserved
stores from that list explicitly.
As mentioned above, you do not get to select the name or the type of a reserved store (though we anticipate that you will be able configure the store type in a future release).
The reserved stores must be of type filesystem. Hence, you must
provide configuration for them in your glance-api.conf
file. You
do this by introducing a section in glance-api.conf
for each reserved
store as follows:
[os_glance_tasks_store]
filesystem_store_datadir = /var/lib/glance/tasks_work_dir
[os_glance_staging_store]
filesystem_store_datadir = /var/lib/glance/staging
Since these are both filesystem stores (remember, you do not get a choice)
the only option you must configure for each is the
filesystem_store_datadir
. Please keep the following points in mind:
The path for filesystem_store_datadir
used for the reserved
stores must be different from the path you are using for
any filesystem store you have listed in enabled_backends
.
Using the same data directory for multiple filesystem stores is
unsupported and may lead to data loss.
The identifiers for reserved stores, that is, os_glance_tasks_store
and os_glance_staging_store
, must not be included in the
enabled_backends
list.
The reserved stores will not appear in the store discovery response
or as values in the OpenStack-image-store-ids
response header of
the image-create call.
The reserved stores will not be accepted as the value of the
X-Image-Meta-Store
header on the image-data-upload call or
the image-import call.
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