Chapter 5. Technology previews

This section provides an overview of Technology Preview features introduced or updated in this release of Red Hat Ceph Storage.


Technology Preview features are not supported with Red Hat production service level agreements (SLAs), might not be functionally complete, and Red Hat does not recommend to use them for production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information on Red Hat Technology Preview features support scope, see the Technology Preview Features Support Scope.

  • Bucket granular multi-site replication [Technology Preview]

    Previously, all buckets within a zone group were mirror copies that contained the same data. Multisite data flow occurred within and between zones. With this release, bucket granular multisite replication enables you to control the flow and replication of data at the bucket level. Buckets within a zone may contain different data, and can pull data from other buckets in other zones.

  • Document how to filter content with a query via a comma-separated values (CSV) file when retrieving data with S3 objects [Technology Preview]

    The S3 Select Object Content API is now supported as a Technology Preview. This API filters the content of an S3 object through the structured query language (SQL). In the request you must specify the data serialization format that is comma-separated values (CSV) of the S3 object to retrieve the specified content. Aws CLI Select Object Content uses the CSV format to parse object data into records and returns only the records specified in the query.

5.1. Ceph Object Gateway

Ceph object gateway in multisite replication setup now supports a subset of AWS bucket replication API functionality

With this release, Ceph Object Gateway now supports a subset of AWS bucket replication API functionality including {Put, Get, Delete} Replication operations. This feature enables bucket-granularity replication and additionally provides end-user replication control with the caveat that currently, buckets can be replicated within zones in an existing CephObject Gateway multisite replication setup.

Technology preview support for KMIP-protocol key management servers

With this release, technology preview support is available for KMIP-protocol key management servers like IBM SKLM thereby expanding the range of popular key management software used with Ceph object gateway’s managed encryption feature.

5.2. RADOS Block Devices (RBD)

librbd PMEM-based persistent write-back cache to reduce latency

With this release, the new pwl_cache librbd plugin provides a log-structured write-back cache targeted at PMEM devices thereby reducing the latency. The updates to the image are batched and flushed in-order, retaining the actual image in a crash-consistent state. If the PMEM device is lost, the image is still accessible though it may appear outdated.

Snapshot quiesce hook support for rbd-nbd devices

With this release, librbd API now offers quiesce and unquiesce hooks that enable coordinated snapshot creation. The rbd-nbd daemon optionally freezes and thaws the file system mounted on top of the mapped device to create file system consistent snapshots. This behavior can be customized by editing the rbd-nbd_quiesce shell script or by replacing it with a custom executable.