[Openstack] How does VMs connect to cinder created Volumes ?

Razique Mahroua razique.mahroua at gmail.com
Wed Dec 5 10:22:12 UTC 2012

Hey man,
actually, the server which runs the cinder-volume services expects a LVM volume group - and depending on the driver you are using, a LV is carved out and exposed (let's say via iscsi) to the node which runs the instance.
The compute driver attaches that volume to the running instance afterwards, so the instance only sees a raw volume you'd add a filesytem into : 
You can add a layer by holding that LVM volume somewhere else, making one another exposition from the place the VG is to the controller
LVM PV |-----> VG ----> Cinder manages the LV ----> ISCSI (whatever) Exposition to the compute node -----> Compute driver adds that volume to the instance -----> Which sees it as a raw volume

Razique Mahroua - Nuage & Co
razique.mahroua at gmail.com
Tel : +33 9 72 37 94 15

Le 5 déc. 2012 à 10:53, Skible OpenStack <skible.openstack at gmail.com> a écrit :

> Hello everyone,
> I have cinder installed on my controller node, can anyone explain to me how a VM becomes aware of the volume ?
> After all a VM is launched on a node different than the controller one so if the VM wants to store something on the Volume, does it have to send the data to the controller node which in his turn will save the data on the volume using cinder or is there a direct connection between the VM and the volume after allocation, if yes, is this connection on the hypervisor level or what level exaclty?
> Thanks, really appreciate it if you can help me out there !
> Best regards
> Fellow Stacker
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