Add iSCSI based storage

This section describes how to add storage from a SAN based on iSCSI.

Install open-iscsi

Open-iscsi might already be installed

sudo apt install open-iscsi lvm2 thin-provisioning-tools

We might already be using iSCSI if cinder is set up with LVM

Prepare node for cinder-volumes from iSCSI SAN

sudo iscsiadm -m session

Discover iSCSI targets on SAN

sudo iscsiadm -m discovery -t sendtargets -p <SAN_IP>

Login to the target and verify a session

sudo iscsiadm -m node -T <TARGET_IQN> -p <SAN_IP> --login
sudo iscsiadm -m session

Configure the target to automatically connect at boot

sudo iscsiadm -m node -T <TARGET_IQN> -p <SAN_IP> --op=update -n node.startup -v automatic

Identify disk device for iSCSI lun / volume

To create a PV on the host for the iSCSI disk we need to identify the disk

sudo iscsiadm -m session
sudo lsblk -o NAME,SIZE,HCTL,TYPE,MOUNTPOINT

I know that the size of the disk sdc corresponds with the iSCSI LUN.

Another way is to use sudo ls -l /dev/disk/by-id/scsi* which lists all disk devices by id. In here I can search for references to my SAN and the lun name used (vol04 in my example)

Best practice is to use this id instead of the /dev/sdX name from lsblk

Update LVM config to allow by-id

If you want to use the by-id identifier and you've already configured LVM filters for /dev/sdX we'll need to update the LVM config. If not, at least add the "a/dev/disk/by-id/.*/" portion

/etc/lvm/lvm.conf

...
devices {
  filter = [ "a/sda/", "a/sdb/", "a/dev/disk/by-id/.*", "r/.*/"]
  ...
}

Create PV and VG for iSCSI volume

Now let's create a physical volume on our host from this iSCSI disk

sudo pvcreate /dev/disk/by-id/scsi-<iqn>-<identifier>

And create a volume group and add the pv

sudo vgcreate <VG_NAME> /dev/disk/by-id/scsi-<iqn>-<identifier>

Cinder configuration for iSCSI

We assume here that the cinder-volume service is installed on the storage node

[DEFAULT]
...
enabled_backends = iscsi_lvm #Additional services can be configured

[iscsi_lvm]
volume_driver = cinder.volume.drivers.lvm.LVMVolumeDriver
volume_group = cinder-iscsi-vg       # your SAN VG name
target_protocol = iscsi
target_helper = lioadm
volume_backend_name = iscsi_lvm

Restart cinder volume service

sudo systemctl restart cinder-volume.service

Verify that the volume service is registered

On the controller

. admin-openrc
openstack volume service list

<!--

Update cinder-scheduler config

On the controller

/etc/cinder/cinder.conf

Update enabled_backends

[DEFAULT]
...
enabled_backends = lvm,iscsi_lvm,nfs
``` -->

## Create volume type and test volume creation

Create a volume type named ```sanvol``` based on the backend ```lvm_iscsi```

```bash
openstack volume type create --property volume_backend_name=lvm_iscsi sanvol

Test creation of a volume

openstack volume create --type sanvol --size 1 test-san

Verify on the storage node

sudo lvs
sudo lvdisplay <LVPATH>

Note that the ID listed in Openstack/Cinder corresponds with the lvname

Use iSCSI on compute node

So the flow for a VM running on node 2 would be (node-1 is the storage node)

Verify iscsi is running on node 2 and that it can list the target on node 1

sudo systemctl start iscsid
sudo systemctl status iscsid

Verify that we can see target from node-1

sudo iscsiadm -m discovery -t sendtargets -p <COMPUTE-1>

Test creation of VM on iSCSI

Upload image to volume named ubu-iscsi-1

openstack volume create --size 20 --image ubuntu-24.04 --type sanvol ubu-iscsi-2

Wait for it to be available

openstack volume show ubu-iscsi-2

Create server based on this volume

openstack server create --flavor test.medium --volume ubu-iscsi-2 --nic net-id=$(openstack network list -f value -c ID | head -1) ubu-iscsi-2

lsblk view

lsblk will also list the volumes created

Add disk to iSCSI target

If an additional disk surfaces on the iSCSI target this will be listed as a disk device on the storage node

sudo lsblk
sudo ls -l /dev/disk/by-id/scsi*

To utilize this disk we'll again have to create a pv for it and add it to a volume group

Create the pv as previously

sudo pvcreate /dev/disk/by-id/scsi<DISK>

Instead of creating a volume group we'll extend the existing one by adding the new pv

sudo pvs
sudo vgextend <VG_NAME> <PV_NAME>