Great! Some more folowups:) 1. In what stack is the driver used in that case if QEMU communicates directly with librados? 2. With QEMU-librados I would guess the new kernel targets/LIO would not work? They give better performance and lower CPU.. 3. Where is the kernel driver used in that case?.. 4. In QEMU, is it a SCSI device? MW Mukul On Mon, Oct 13, 2014 at 6:44 AM, Robert Sander <r.sander@xxxxxxxxxxxxxxxxxxx> wrote: > On 10.10.2014 02:19, Marcus White wrote: >> >> For VMs, I am trying to visualize how the RBD device would be exposed. >> Where does the driver live exactly? If its exposed via libvirt and >> QEMU, does the kernel driver run in the host OS, and communicate with >> a backend Ceph cluster? If yes, does libRBD provide a target (SCSI?) >> interface which the kernel driver connects to? Trying to visualize >> what the stack looks like, and the flow of IOs for block devices. > > For VMs, the RBD is not exposed at all. The communication is made in > userland space of the host kernel, qemu uses librados directly, no > kernel driver involved. > > The VM guest kernel sees a virtual block device presented by qemu. > > Regards > -- > Robert Sander > Heinlein Support GmbH > Schwedter Str. 8/9b, 10119 Berlin > > http://www.heinlein-support.de > > Tel: 030 / 405051-43 > Fax: 030 / 405051-19 > > Zwangsangaben lt. §35a GmbHG: > HRB 93818 B / Amtsgericht Berlin-Charlottenburg, > Geschäftsführer: Peer Heinlein -- Sitz: Berlin > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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