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[Ahmed Al-Mehdi <ahmed@xxxxxxxxxx>]

Hello,

My question is specific to nova-volume, but might apply to Cinder also.  In the "OpenStack Install and Deploy Manual - Ubuntu" doc, Page 47 lists the nova.conf file.  In it the "VOLUME" related section is
noted below:


# VOLUMES

volume_group=nova-volumes

volume_name_template=volume-%08x

iscsi_helper=tgtadm



Who manages LVM VG - "nova-volumes".  Is it nova-volume module or the iSCSI Target.  I am guessing nova-volume.   My thinking is nova-volume creates LV out of this VG and feeds it into iSCSI Target using utilites - tgt-admin, tgt-setup-lun (etc.).  This LV is then exported as a block storage by the iSCSI Target.  This block  storage is then attached to / seen by a VM instance on the same or another physical host which has iSCSI connection to the SCSI Tgt. Would that be correct?

If so, I have a few questions:
 - What if I want to "feed" additional disks/block devices or VGs to nova-volume module?  How and where would I specify that.  Or do I have to modify the nova-volume code to handle that.  (One solution I can think of is to pool the additional storage into the existing VG - nova-volumes.)
 - What if I don't want to feed any VG to nova-volume, but rather want nova-volume to call into the iSCSI target  to get block storage.
 - I would like to understand the interaction/interface/API  of nova-volume (Cinder) that calls into iSCSI Target to expose storage or API to storage appliance to get block storage.    Is this a generic standardized API that can call into any type of block storage - iSCSI , FCoE, etcv?   If so, pointers to API would be highly appreciated.

I apologize if my questions seems newbie'ish or confusing as I am trying to understand the inner workings of nova-volume/Cinder.  Any help is highly appreciated.

Regards,
Ahmed.