On Tue, Mar 18, 2014 at 11:01 AM, Zhangleiqiang (Trump) <zhangleiqi...@huawei.com> wrote: >> From: Huang Zhiteng [mailto:winsto...@gmail.com] >> 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) >> <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. > > 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.
Set clustering use case and performance improvement aside, what other benefits/use cases can RDM bring/be useful for? > >> > 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 > _______________________________________________ > 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
