Cinder in Kolla

Overview

Currently Kolla can deploy the cinder services:

  • cinder-api
  • cinder-scheduler
  • cinder-backup
  • cinder-volume

The cinder implementation defaults to using LVM storage. The default implementation requires a volume group be set up. This can either be a real physical volume or a loopback mounted file for development.

Note

The Cinder community has closed a bug as WontFix which makes it impossible for LVM to be used at all in a multi-controller setup. The only option for multi-controller storage to work correctly at present is via a Ceph deployment. If community members disagree with this decision, please report the specific use case in the Cinder bug tracker here: _bug 1571211.

Create a Volume Group

When using the lvm backend, a volume group will need to be created on each storage node. Use pvcreate and vgcreate to create the volume group. For example with the devices /dev/sdb and /dev/sdc:

<WARNING ALL DATA ON /dev/sdb and /dev/sdc will be LOST!>

pvcreate /dev/sdb /dev/sdc
vgcreate cinder-volumes /dev/sdb /dev/sdc

During development, it may be desirable to use file backed block storage. It is possible to use a file and mount it as a block device via the loopback system.

free_device=$(losetup -f)
fallocate -l 20G /var/lib/cinder_data.img
losetup $free_device /var/lib/cinder_data.img
pvcreate $free_device
vgcreate cinder-volumes $free_device

Enable the lvm backend in /etc/kolla/globals.yml:

enable_cinder_backend_lvm: "yes"

Validation

Create a volume as follows:

$ openstack volume create --size 1 steak_volume
<bunch of stuff printed>

Verify it is available. If it says “error” here something went wrong during LVM creation of the volume.

$ openstack volume list
+--------------------------------------+--------------+-----------+------+-------------+
| ID                                   | Display Name | Status    | Size | Attached to |
+--------------------------------------+--------------+-----------+------+-------------+
| 0069c17e-8a60-445a-b7f0-383a8b89f87e | steak_volume | available |    1 |             |
+--------------------------------------+--------------+-----------+------+-------------+

Attach the volume to a server using:

openstack server add volume steak_server 0069c17e-8a60-445a-b7f0-383a8b89f87e

Check the console log added the disk:

openstack console log show steak_server

A /dev/vdb should appear in the console log, at least when booting cirros. If the disk stays in the available state, something went wrong during the iSCSI mounting of the volume to the guest VM.

Cinder LVM2 back end with iSCSI

As of Newton-1 milestone, Kolla supports LVM2 as cinder back end. It is accomplished by introducing two new containers tgtd and iscsid. tgtd container serves as a bridge between cinder-volume process and a server hosting Logical Volume Groups (LVG). iscsid container serves as a bridge between nova-compute process and the server hosting LVG.

In order to use Cinder’s LVM back end, a LVG named cinder-volumes should exist on the server and following parameter must be specified in globals.yml

enable_cinder_backend_lvm: "yes"

For Ubuntu and LVM2/iSCSI

iscsd process uses configfs which is normally mounted at /sys/kernel/config to store discovered targets information, on centos/rhel type of systems this special file system gets mounted automatically, which is not the case on debian/ubuntu. Since iscsid container runs on every nova compute node, the following steps must be completed on every Ubuntu server targeted for nova compute role.

  • Add configfs module to /etc/modules

  • Rebuild initramfs using: update-initramfs -u command

  • Stop open-iscsi system service due to its conflicts with iscsid container.

    Ubuntu 16.04 (systemd): systemctl stop open-iscsi; systemctl stop iscsid

  • Make sure configfs gets mounted during a server boot up process. There are multiple ways to accomplish it, one example:

    mount -t configfs /etc/rc.local /sys/kernel/config

Cinder back end with external iSCSI storage

In order to use external storage system (like one from EMC or NetApp) the following parameter must be specified in globals.yml

enable_cinder_backend_iscsi: "yes"

Also enable_cinder_backend_lvm should be set to “no” in this case.