> From: Huang Zhiteng [mailto:[email protected]] > Sent: Tuesday, March 18, 2014 10:32 AM > To: OpenStack Development Mailing List (not for usage questions) > Subject: Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device > Mapping > > On Tue, Mar 18, 2014 at 9:40 AM, Zhangleiqiang (Trump) > <[email protected]> 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.
Yes. "Clustering" include Oracle RAC, MSCS, etc. If they want to work in instance-based cloud environment, RDM and multi-attached-volumes are both needed. But RDM is not only used for clustering, and haven't dependency for 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 > > [email protected] > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > -- > Regards > Huang Zhiteng > > _______________________________________________ > OpenStack-dev mailing list > [email protected] > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev _______________________________________________ OpenStack-dev mailing list [email protected] http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
