[Openstack] IO flow on multi-node setup

Bernd Bausch berndbausch at gmail.com
Fri Oct 26 14:42:12 UTC 2018

You configure an LVM volume group for each Cinder backend. A CInder
volume on that backend corresponds to an LVM volume in that volume
group. The LVM volume is exposed as an iSCSI target, usually via LIO,
but I believe this is configurable. The compute node uses /iscsiadm /to
import that volume as a SCSI device and connects that device to the VM.

I don't know if this is documented anywhere, but it's easy and fun to
explore. On the storage node, use LVM commands to look into volume
groups and volumes, and the /tgtadm /command to check targets. On the
compute node, list all SCSI disks, use /iscsiadm -m session /to check
iSCSI sessions, and use /virsh domblklist /and /virsh edit /(assuming
your hypervisor is libvirt-controlled) to confirm that the iSCSI LUN is
connected to the VM.

On 10/26/2018 10:03 PM, Tushar Tyagi wrote:
> I am using Rocky release and configuring for NVMe backend with LVM. Can you please tell me how this one might flow, or redirect me to the documentation?
> I have not been able to found much documentation regarding this.

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