%openstack; ]> 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. OpenStack Block Storage 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. Configure the OpenStack Compute and the OpenStack Block Storage services through the cinder.conf file. Use the cinder create command to create a volume. This command creates an LV into the volume group (VG) cinder-volumes. Use the nova volume-attach command to attach the volume to an instance. 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. The network mode does not interfere with OpenStack Block Storage operations, but you must set up networking for Block Storage 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, you can store and run instances from inside volumes. For information, see the Launch an instance from a volume section in the OpenStack End User Guide.

The default iscsi_helper tool is tgtadm. To use LIO iSCSI, install the python-rtslib package, and set iscsi_helper=lioadm in the cinder.conf file. Once configured, you can use the cinder-rtstool command to manage the volumes. This command enables you to create, delete, and verify volumes and determine targets and add iSCSI initiators to the system.

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