Customer wants to be able to attach Raw devices to instances, this allows in the meantime to attach storage which will perform faster and it's replicated on different layer, so it doesn't require the overhead of OSP storage backends (ceph replication, etc).


+++ This bug was initially created as a clone of Bug #1057319 +++

Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/support-for-raw-device-mapping.

Description:

In comparison with VMware, openstack cannot support the feature of Raw Device Mapping(RDM).

With RDM, the storage logical unit number (LUN) can be directly connected to a instance or VM from the storage area network (SAN).

For most data center applications, including databases, customer relationship management (CRM)applications and enterprise resource planning (ERP) applications, RDM can be used for configurations involving clustering between virtual machines, between physical and virtual machines or where SAN-aware applications are running inside a virtual machine.

RDM, which permits the use of existing SAN commands, is generally used to improve performance in I/O-intensive applications and block locking. Physical mode provides access to most hardware functions of the storage system that is mapped.

with the configuration of the instace:
<disk type="block" device="lun" sgio="unfiltered">
    <driver name="qemu" type="raw" cache="none" />
    <source dev="/dev/sdb" />
    <target dev="sda" bus="scsi" />
    <shareable />
</disk>

<controller type='scsi' model='virtio-scsi'/>

The device /dev/sdb or LUN in the physical server can be connected by the instance.For example, running the command "sg_inq /dev/sda" in the guest.


Specification URL (additional information):

None