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264 lines
8.3 KiB
ReStructuredText
==================================
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Pool Placement and Storage Classes
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==================================
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.. contents::
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Placement Targets
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=================
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.. versionadded:: Jewel
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Placement targets control which `Pools`_ are associated with a particular
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bucket. A bucket's placement target is selected on creation, and cannot be
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modified. The ``radosgw-admin bucket stats`` command will display its
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``placement_rule``.
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The zonegroup configuration contains a list of placement targets with an
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initial target named ``default-placement``. The zone configuration then maps
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each zonegroup placement target name onto its local storage. This zone
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placement information includes the ``index_pool`` name for the bucket index,
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the ``data_extra_pool`` name for metadata about incomplete multipart uploads,
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and a ``data_pool`` name for each storage class.
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.. _storage_classes:
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Storage Classes
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===============
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.. versionadded:: Nautilus
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Storage classes are used to customize the placement of object data. S3 Bucket
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Lifecycle rules can automate the transition of objects between storage classes.
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Storage classes are defined in terms of placement targets. Each zonegroup
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placement target lists its available storage classes with an initial class
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named ``STANDARD``. The zone configuration is responsible for providing a
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``data_pool`` pool name for each of the zonegroup's storage classes.
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Zonegroup/Zone Configuration
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============================
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Placement configuration is performed with ``radosgw-admin`` commands on
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the zonegroups and zones.
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The zonegroup placement configuration can be queried with:
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::
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$ radosgw-admin zonegroup get
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{
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"id": "ab01123f-e0df-4f29-9d71-b44888d67cd5",
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"name": "default",
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"api_name": "default",
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...
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"placement_targets": [
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{
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"name": "default-placement",
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"tags": [],
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"storage_classes": [
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"STANDARD"
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]
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}
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],
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"default_placement": "default-placement",
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...
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}
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The zone placement configuration can be queried with:
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::
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$ radosgw-admin zone get
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{
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"id": "557cdcee-3aae-4e9e-85c7-2f86f5eddb1f",
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"name": "default",
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"domain_root": "default.rgw.meta:root",
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...
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"placement_pools": [
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{
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"key": "default-placement",
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"val": {
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"index_pool": "default.rgw.buckets.index",
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"storage_classes": {
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"STANDARD": {
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"data_pool": "default.rgw.buckets.data"
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}
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},
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"data_extra_pool": "default.rgw.buckets.non-ec",
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"index_type": 0,
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"inline_data": true
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}
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}
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],
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...
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}
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.. note:: If you have not done any previous `Multisite Configuration`_,
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a ``default`` zone and zonegroup are created for you, and changes
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to the zone/zonegroup will not take effect until the Ceph Object
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Gateways are restarted. If you have created a realm for multisite,
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the zone/zonegroup changes will take effect once the changes are
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committed with ``radosgw-admin period update --commit``.
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Adding a Placement Target
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-------------------------
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To create a new placement target named ``temporary``, start by adding it to
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the zonegroup:
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::
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$ radosgw-admin zonegroup placement add \
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--rgw-zonegroup default \
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--placement-id temporary
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Then provide the zone placement info for that target:
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::
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$ radosgw-admin zone placement add \
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--rgw-zone default \
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--placement-id temporary \
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--data-pool default.rgw.temporary.data \
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--index-pool default.rgw.temporary.index \
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--data-extra-pool default.rgw.temporary.non-ec
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.. note:: With default placement target settings, RGW stores an object's first data chunk in the RADOS "head" object along
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with xattr metadata. The `--placement-inline-data=false` flag may be passed with the `zone placement add` or
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`zone placement modify` commands to change this behavior for new objects stored on the target.
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When data is stored inline (default), it may provide an advantage for read/write workloads since the first chunk of
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an object's data can be retrieved/stored in a single librados call along with object metadata. On the other hand, a
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target that does not store data inline can provide a performance benefit for RGW client delete requests when
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the BlueStore DB is located on faster storage than bucket data since it eliminates the need to access
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slower devices synchronously while processing the client request. In that case, data associated with the deleted
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objects is removed asynchronously in the background by garbage collection.
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.. _adding_a_storage_class:
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Adding a Storage Class
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----------------------
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To add a new storage class named ``GLACIER`` to the ``default-placement`` target,
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start by adding it to the zonegroup:
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::
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$ radosgw-admin zonegroup placement add \
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--rgw-zonegroup default \
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--placement-id default-placement \
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--storage-class GLACIER
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Then provide the zone placement info for that storage class:
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::
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$ radosgw-admin zone placement add \
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--rgw-zone default \
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--placement-id default-placement \
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--storage-class GLACIER \
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--data-pool default.rgw.glacier.data \
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--compression lz4
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Customizing Placement
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=====================
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Default Placement
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-----------------
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By default, new buckets will use the zonegroup's ``default_placement`` target.
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This zonegroup setting can be changed with:
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::
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$ radosgw-admin zonegroup placement default \
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--rgw-zonegroup default \
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--placement-id new-placement
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User Placement
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--------------
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A Ceph Object Gateway user can override the zonegroup's default placement
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target by setting a non-empty ``default_placement`` field in the user info.
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Similarly, the ``default_storage_class`` can override the ``STANDARD``
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storage class applied to objects by default.
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::
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$ radosgw-admin user info --uid testid
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{
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...
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"default_placement": "",
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"default_storage_class": "",
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"placement_tags": [],
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...
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}
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If a zonegroup's placement target contains any ``tags``, users will be unable
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to create buckets with that placement target unless their user info contains
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at least one matching tag in its ``placement_tags`` field. This can be useful
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to restrict access to certain types of storage.
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The ``radosgw-admin`` command can modify these fields directly with:
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::
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$ radosgw-admin user modify \
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--uid <user-id> \
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--placement-id <default-placement-id> \
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--storage-class <default-storage-class> \
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--tags <tag1,tag2>
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.. _s3_bucket_placement:
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S3 Bucket Placement
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-------------------
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When creating a bucket with the S3 protocol, a placement target can be
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provided as part of the LocationConstraint to override the default placement
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targets from the user and zonegroup.
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Normally, the LocationConstraint must match the zonegroup's ``api_name``:
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::
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<LocationConstraint>default</LocationConstraint>
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A custom placement target can be added to the ``api_name`` following a colon:
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::
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<LocationConstraint>default:new-placement</LocationConstraint>
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Swift Bucket Placement
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----------------------
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When creating a bucket with the Swift protocol, a placement target can be
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provided in the HTTP header ``X-Storage-Policy``:
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::
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X-Storage-Policy: new-placement
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Using Storage Classes
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=====================
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All placement targets have a ``STANDARD`` storage class which is applied to
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new objects by default. The user can override this default with its
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``default_storage_class``.
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To create an object in a non-default storage class, provide that storage class
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name in an HTTP header with the request. The S3 protocol uses the
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``X-Amz-Storage-Class`` header, while the Swift protocol uses the
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``X-Object-Storage-Class`` header.
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When using AWS S3 SDKs such as ``boto3``, it is important that non-default
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storage class names match those provided by AWS S3, or else the SDK
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will drop the request and raise an exception.
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S3 Object Lifecycle Management can then be used to move object data between
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storage classes using ``Transition`` actions.
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.. _`Pools`: ../pools
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.. _`Multisite Configuration`: ../multisite
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