Red Hat SummitChapter 3. Block storage
Red Hat Ceph Storage uses block storage, and refers to this as Ceph Block Devices. Block-based storage interfaces are the most common way to store data with rotating media such as hard drives and flash storage (SSDs and HDDs).
Ceph Block Devices interact with OSDs by using the librbd library.
Ceph Block Devices deliver high performance with infinite scalability to Kernel Virtual Machines (KVMs), such as Quick Emulator (QEMU), and cloud-based computing systems, like OpenStack, that rely on the libvirt and QEMU utilities to integrate with Ceph Block Devices. You can use the same storage cluster to operate the Ceph Object Gateway and Ceph Block Devices simultaneously.
Ceph Block Devices can easily be managed through either the Ceph dashboard or command-line interface (CLI) commands. For detailed information about Ceph Block Devices, see Introduction to Ceph block devices.
3.1. Block storage common workloads
Understand the most common workloads for Ceph Block Device.
- Database store
- Use for data protection application database backup.
- Device mirroring
- Use to protect against data loss or site failures.
- Data resiliency
- Use for replication and erasure coding.
3.2. Getting started with block storage
This section lists the relevant tasks required for working with block storage.
Managing Ceph Block Devices with the dashboard
Manage Ceph Block Devices by using the Red Hat Ceph Storage dashboard. As a storage administrator, you can manage and monitor block device images on the Red Hat Ceph Storage dashboard. The functionality is divided between generic image functions and mirroring functions. For example, you can create new images, view the state of images that are mirrored across clusters, and set IOPS limits on an image.
For detailed information, see Management of block devices using the Ceph dashboard.
Common block storage CLI commands
This information is for a quick reference of basic block image CLI commands. For a full list and more detailed information about each command, see Introduction to Ceph block devices.
Creating images
Syntax
rbd create IMAGE_NAME --size MEGABYTES --pool POOL_NAMEImportantA pool must be created before creating a block image. For details, see Creating a block device pool.
Listing images
Syntax
rbd ls POOL_NAMERetrieving image information from a particular image in the default pool
Syntax
rbd --image IMAGE_NAME infoRetrieving information from an image within a pool.
Syntax
rbd --image IMAGE_NAME -p POOL_NAME infoResizing images.
Increasing the maximum size of a Ceph Block Device image for the default
rbdpool.Syntax
rbd resize --image IMAGE_NAME --size SIZEIncreasing the maximum size of a Ceph Block Deivce image for a specific pool.
Syntax
rbd resize --image POOL_NAME/IMAGE_NAME --size SIZEDecreasing the maximum size of a Ceph Block Device image for the default
rbdpool.Syntax
rbd resize --image IMAGE_NAME --size SIZE --allow-shrinkDecreasing the maximum size of a Ceph Block Device image for a specific pool.
Syntax
rbd resize --image POOL_NAME/IMAGE_NAME --size SIZE --allow-shrink
Moving images to the trash.
Syntax
rbd trash mv POOL_NAME/IMAGE_NAMERestoring an image from the trash.
Syntax
rbd trash restore POOL_NAME/IMAGE_NAMEEnsuring the
rbd_supportCeph Manager module is enabled.Syntax
ceph mgr module ls
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