OpenStack Cinder iSCSI

OpenStack is an open-source cloud computing platform that allows users to manage and control a pool of computing resources. One of the core components of OpenStack is Cinder, which provides block storage services to virtual machines (VMs) running on the platform. In this article, we will explore the iSCSI protocol used by Cinder for communication and how to configure it.

Introduction to iSCSI

iSCSI (Internet Small Computer System Interface) is a protocol that allows users to send SCSI commands over an IP network, enabling the use of remote storage devices as if they were locally attached. It provides block-level access to storage resources, making it suitable for applications that require direct access to disks.

With iSCSI, the storage server (iSCSI target) exposes one or more LUNs (Logical Unit Numbers) to the client (iSCSI initiator) over the network. The initiator can then attach the LUNs and use them as local storage devices. This allows VMs running on the OpenStack platform to access remote storage resources made available by Cinder.

Configuring Cinder for iSCSI

To configure Cinder for iSCSI, you need to make changes to the Cinder configuration file, usually located at /etc/cinder/cinder.conf. Here are the steps to follow:

  1. Enable iSCSI in the Cinder configuration file by setting the enabled_backends option to include the iSCSI backend. For example:
[DEFAULT]
enabled_backends = lvm,iscsi
  1. Configure the iSCSI backend by adding a new section to the configuration file. Specify the iSCSI driver class, target IP address, target port, and other required parameters. For example:
[iscsi]
volume_driver = cinder.volume.drivers.lvm.LVMVolumeDriver
iscsi_protocol = iscsi
iscsi_helper = lioadm
volume_group = cinder-volumes
target_ip_address = 192.168.1.10
target_port = 3260
  1. Restart the Cinder service to apply the changes. Use the following command:
$ sudo service cinder-volume restart

Once the iSCSI backend is configured, Cinder will be able to manage iSCSI volumes and attach them to the VMs as needed.

Using iSCSI Volumes in OpenStack

To use iSCSI volumes in OpenStack, you need to create a volume and attach it to a VM. Here's an example using the OpenStack command-line interface (CLI):

  1. Create a volume using the openstack volume create command. Specify the size of the volume in gigabytes and the availability zone. For example:
$ openstack volume create --size 10 --availability-zone nova volume1
  1. Attach the volume to a VM using the openstack server add volume command. Specify the instance ID and the volume ID. For example:
$ openstack server add volume instance1 volume1
  1. Log in to the VM and use the lsblk command to verify that the volume is attached. You should see a new block device representing the attached volume. For example:
$ ssh instance1
$ lsblk

You can then use the attached iSCSI volume as a local disk within the VM.

Conclusion

In this article, we explored the iSCSI protocol used by OpenStack Cinder for block storage. We learned how to configure Cinder for iSCSI and how to use iSCSI volumes in OpenStack. iSCSI provides a flexible and efficient way to manage remote storage resources, enabling VMs to access them as if they were locally attached disks.