Multi Store Support¶
The Multi Store feature was introduced as EXPERIMENTAL in Rocky and is now fully supported in the Train release.
Scope of this document¶
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
In this section, we discuss what configuration options are available to operators to enable multiple stores support.
enabled_backendsmust 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
vmware. In order to have multiple stores operator can specify multiple key:value separated by comma.
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/infocall, where an http type store will have the attribute
read-only: Truein addition to the usual
[DEFAULT] enabled_backends = fast:rbd, cheap:rbd, shared:file, reliable:file
default_backendmust be set to one of the identifier which are defined using
default_backendis 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_backendssection 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
store_descriptionis 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.
Store Configuration Issues¶
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.
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
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
Currently, there are two reserved stores:
This store is used for the tasks engine. It replaces the use of the DEPRECATED configuration option
This store is used for the staging area for the interoperable image import process. It replaces the use of the DEPRECATED configuration option
If end user wants to retrieve all the available stores using
CONF.enabled_backends then they need 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:
filesystem_store_datadir = /var/lib/glance/tasks_work_dir
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_datadirused 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_staging_store, must not be included in the
The reserved stores will not appear in the store discovery response or as values in the
OpenStack-image-store-idsresponse header of the image-create call.
The reserved stores will not be accepted as the value of the
X-Image-Meta-Storeheader on the image-data-upload call or the image-import call.