The OpenStack Block Storage service works through the interaction of a series of daemon processes named cinder-* that reside persistently on the host machine or machines. The binaries can all be run from a single node, or spread across multiple nodes. They can also be run on the same node as other OpenStack services.

To administer the OpenStack Block Storage service, it is helpful to understand a number of concepts. You must make certain choices when you configure the Block Storage service in OpenStack. The bulk of the options come down to two choices, single node or multi-node install. You can read a longer discussion about storage decisions in Storage Decisions in the OpenStack Operations Guide. The OpenStack Block Storage Service enables you to add extra block-level storage to your OpenStack Compute instances. This service is similar to the Amazon EC2 Elastic Block Storage (EBS) offering.

The default OpenStack Block Storage service implementation is an iSCSI solution that uses Logical Volume Manager (LVM) for Linux. The OpenStack Block Storage service is not a shared storage solution like a Storage Area Network (SAN) of NFS volumes, where you can attach a volume to multiple servers. With the OpenStack Block Storage service, you can attach a volume to only one instance at a time. The OpenStack Block Storage service also provides drivers that enable you to use several vendors' back-end storage devices, in addition to or instead of the base LVM implementation. This high-level procedure shows you how to create and attach a volume to a server instance. You must configure both OpenStack Compute and the OpenStack Block Storage service through the cinder.conf file. Create a volume through the cinder create command. This command creates an LV into the volume group (VG) cinder-volumes. Attach the volume to an instance through the nova volume-attach command. This command creates a unique iSCSI IQN that is exposed to the compute node. The compute node, which runs the instance, now has an active ISCSI session and new local storage (usually a /dev/sdX disk). libvirt uses that local storage as storage for the instance. The instance gets a new disk (usually a /dev/vdX disk). For this particular walk through, one cloud controller runs nova-api, nova-scheduler, nova-objectstore, nova-network and cinder-* services. Two additional compute nodes run nova-compute. The walk through uses a custom partitioning scheme that carves out 60 GB of space and labels it as LVM. The network uses the FlatManager and NetworkManager settings for OpenStack Compute (Nova). The network mode does not interfere with the way cinder works, but you must set up networking for cinder to work. For details, see . To set up Compute to use volumes, ensure that Block Storage is installed along with lvm2. This guide describes how to troubleshoot your installation and back up your Compute volumes.

In some cases, instances can be stored and run from inside volumes. For information, see the Launch an instance from a volume section in the OpenStack End User Guide.

This section provides useful tips to help troubleshoot your Block Storage Service installation.