On Tue, Mar 18, 2014 at 9:40 AM, Zhangleiqiang (Trump) <zhangleiqi...@huawei.com> wrote: > Hi, stackers： > > With RDM, the storage logical unit number (LUN) can be directly > connected to a instance from the storage area network (SAN). > > For most data center applications, including Databases, CRM and ERP > applications, RDM can be used for configurations involving clustering between > instances, between physical hosts and instances or where SAN-aware > applications are running inside a instance. If 'clustering' here refers to things like cluster file system, which requires LUNs to be connected to multiple instances at the same time. And since you mentioned Cinder, I suppose the LUNs (volumes) are managed by Cinder, then you have an extra dependency for multi-attach feature: https://blueprints.launchpad.net/cinder/+spec/multi-attach-volume. > 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. It seems to me that the performance benefit mostly from virtio-scsi, which is just an virtual disk interface, thus should also benefit all virtual disk use cases not just raw device mapping. > > For libvirt driver, RDM feature can be enabled through the "lun" > device connected to a "virtio-scsi" controller: > > <disk type='block' device='lun'> > <driver name='qemu' type='raw' cache='none'/> > <source dev='/dev/mapper/360022a110000ecba5db427db00000023'/> > <target dev='sdb' bus='scsi'/> > <address type='drive' controller='0' bus='0'/> > </disk> > > <controller type='scsi' index='0' model='virtio-scsi'/> > > Currently，the related works in OpenStack as follows: > 1. block-device-mapping-v2 extension has already support the "lun" > device with "scsi" bus type listed above, but cannot make the disk use > "virtio-scsi" controller instead of default "lsi" scsi controller. > 2. libvirt-virtio-scsi-driver BP ([1]) whose milestone target is > icehouse-3 is aim to support generate a virtio-scsi controller when using an > image with "virtio-scsi" property, but it seems not to take boot-from-volume > and attach-rdm-volume into account. > > I think it is meaningful if we provide the whole support for RDM > feature in OpenStack. > > Any thoughts? Welcome any advices. > > > [1] https://blueprints.launchpad.net/nova/+spec/libvirt-virtio-scsi-driver > ---------- > zhangleiqiang (Trump) > > Best Regards > > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
-- Regards Huang Zhiteng _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
