Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
In general, abstracting the offload of snapshot, backup etc the a SAN is exactly the job of cinder. RDM has, in the general cloud case, a bunch of security issues (raw sector reads outside of what is being presented, firmware updates, etc) that need carefully looking at. On 18 March 2014 09:33, Zhangleiqiang (Trump) wrote: >> From: Huang Zhiteng [mailto:winsto...@gmail.com] >> Sent: Tuesday, March 18, 2014 4:40 PM >> 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 11:01 AM, Zhangleiqiang (Trump) >> 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) >> >> 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? > > Thanks for your reply. > > The advantages of Raw device mapping are all introduced by its capability of > "pass" scsi command to the device, and the most common use cases are > clustering and performance improvement mentioned above. > > And besides these two scenarios, there is another use case: running SAN-aware > application inside instances, such as: > 1. SAN management app > 2. Apps which can offload the device related works, such as snapshot, backup, > etc, to SAN. > > >> > >> >> > 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: >> >> > >> >> > >> >> > >> >> >> >> dev='/dev/mapper/360022a11ecba5db427db0023'/> >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > 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 >> >
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
After second thought, it will be more meaningful to just add virtio-SCSI bus type support to block-device-mapping. RDM can then be used or not, depend on the bus type and device type of bdm specified by user. And user can also just use virtio-SCSI bus for performance other than pass through. Any suggestions? "Zhangleiqiang (Trump)" ： >> From: Huang Zhiteng [mailto:winsto...@gmail.com] >> Sent: Wednesday, March 19, 2014 12:14 PM >> 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 5:33 PM, Zhangleiqiang (Trump) >> wrote: >>>> From: Huang Zhiteng [mailto:winsto...@gmail.com] >>>> Sent: Tuesday, March 18, 2014 4:40 PM >>>> 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 11:01 AM, Zhangleiqiang (Trump) >>>> 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) >>>>>> 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? >>> >>> Thanks for your reply. >>> >>> The advantages of Raw device mapping are all introduced by its capability of >> "pass" scsi command to the device, and the most common use cases are >> clustering and performance improvement mentioned above. >> As mentioned in earlier email, I doubt the performance improvement comes >> from 'virtio-scsi' interface instead of RDM. We can actually test them to >> verify. Here's what I would do: create one LUN(volume) on the SAN, attach >> the volume to instance using current attach code path but change the virtual >> bus to 'virtio-scsi' and then measure the IO performance using standard IO >> benchmark; next, attach the volume to instance using 'lun' device for 'disk' >> and >> 'virtio-scsi' for bus, and do the measurement again. We shall be able to see >> the performance difference if there is any. Since I don't have a SAN to play >> with, could you please do the test and share the results? > > The performance improvement does comes from "virtio-scsi" controller, and is > not caused by using "lun" device instead of "disk" device. > I don't have a usable SAN at present. But from the libvirt's doc ([1]), the > "lun" device behaves identically to "disk" device except that generic SCSI &g
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
> From: Huang Zhiteng [mailto:winsto...@gmail.com] > Sent: Wednesday, March 19, 2014 12:14 PM > 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 5:33 PM, Zhangleiqiang (Trump) > wrote: > >> From: Huang Zhiteng [mailto:winsto...@gmail.com] > >> Sent: Tuesday, March 18, 2014 4:40 PM > >> 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 11:01 AM, Zhangleiqiang (Trump) > >> 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) > >> >> 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? > > > > Thanks for your reply. > > > > The advantages of Raw device mapping are all introduced by its capability of > "pass" scsi command to the device, and the most common use cases are > clustering and performance improvement mentioned above. > > > As mentioned in earlier email, I doubt the performance improvement comes > from 'virtio-scsi' interface instead of RDM. We can actually test them to > verify. Here's what I would do: create one LUN(volume) on the SAN, attach > the volume to instance using current attach code path but change the virtual > bus to 'virtio-scsi' and then measure the IO performance using standard IO > benchmark; next, attach the volume to instance using 'lun' device for 'disk' > and > 'virtio-scsi' for bus, and do the measurement again. We shall be able to see > the performance difference if there is any. Since I don't have a SAN to play > with, could you please do the test and share the results? The performance improvement does comes from "virtio-scsi" controller, and is not caused by using "lun" device instead of "disk" device. I don't have a usable SAN at present. But from the libvirt's doc ([1]), the "lun" device behaves identically to "disk" device except that generic SCSI commands from the instance are accepted and passed through to the physical device. Sorry for misleading. The "RDM" I mentioned in earlier email includes the "lun" device and the "virtio-scsi" controller. Now, the performance improvement comes from "virtio-scsi" controller, however, boot-from a volume using virtio-scsi interface or attach a volume with a new virtio-scsi interface are both unsupported currently. I think add these features is meaningful. And as mentioned in the first email, set the "virtio-scsi" con
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
On Tue, Mar 18, 2014 at 5:33 PM, Zhangleiqiang (Trump) wrote: >> From: Huang Zhiteng [mailto:winsto...@gmail.com] >> Sent: Tuesday, March 18, 2014 4:40 PM >> 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 11:01 AM, Zhangleiqiang (Trump) >> 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) >> >> 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? > > Thanks for your reply. > > The advantages of Raw device mapping are all introduced by its capability of > "pass" scsi command to the device, and the most common use cases are > clustering and performance improvement mentioned above. > As mentioned in earlier email, I doubt the performance improvement comes from 'virtio-scsi' interface instead of RDM. We can actually test them to verify. Here's what I would do: create one LUN(volume) on the SAN, attach the volume to instance using current attach code path but change the virtual bus to 'virtio-scsi' and then measure the IO performance using standard IO benchmark; next, attach the volume to instance using 'lun' device for 'disk' and 'virtio-scsi' for bus, and do the measurement again. We shall be able to see the performance difference if there is any. Since I don't have a SAN to play with, could you please do the test and share the results? > And besides these two scenarios, there is another use case: running SAN-aware > application inside instances, such as: > 1. SAN management app Yes, that is possible if RDM is enable. But I wonder what is the real use case behind this. Even though SAN mgmt app inside instance is able to manage the LUN directly, but it is just a LUN instead of a real SAN, what the instance can do is *limited* to the specific LUN, which doesn't seem very useful IMO. Or are you thinking about creating a big enough LUN for user so they can treat it like a 'virtual' SAN and do all kinds of management stuff to it and even maybe resell it for PaaS use cases? > 2. Apps which can offload the device related works, such as snapshot, backup, > etc, to SAN. Not sure I follow this use cases either, nor do I understand why end users want to do all those operations _inside_ instance instead of utilizing existing infrastructure like Cinder. If the goal behind this is to make traditional IT users happy, I tend to agree with what Duncan said in another thread (http://osdir.com/ml/openstack-dev/2014-03/msg01395.html) > > >> > >> >> > 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 perfo
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
> From: Huang Zhiteng [mailto:winsto...@gmail.com] > Sent: Tuesday, March 18, 2014 4:40 PM > 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 11:01 AM, Zhangleiqiang (Trump) > 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) > >> 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? Thanks for your reply. The advantages of Raw device mapping are all introduced by its capability of "pass" scsi command to the device, and the most common use cases are clustering and performance improvement mentioned above. And besides these two scenarios, there is another use case: running SAN-aware application inside instances, such as: 1. SAN management app 2. Apps which can offload the device related works, such as snapshot, backup, etc, to SAN. > > > >> > 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: > >> > > >> > > >> > > >> > >> dev='/dev/mapper/360022a11ecba5db427db0023'/> > >> > > >> > > >> > > >> > > >> > > >> > > >> > 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-dri > >> > ver > >> > -- > >> > zhangleiqiang (Tr
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
On Tue, Mar 18, 2014 at 11:01 AM, Zhangleiqiang (Trump) 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) >> 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: >> > >> > >> > >> >> dev='/dev/mapper/360022a11ecba5db427db0023'/> >> > >> > >> > >> > >> > >> > >> > 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
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
> 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) > 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: > > > > > > > > dev='/dev/mapper/360022a11ecba5db427db0023'/> > > > > > > > > > > > > > > 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
Re: [openstack-dev] [Nova][Cinder] Feature about Raw Device Mapping
On Tue, Mar 18, 2014 at 9:40 AM, Zhangleiqiang (Trump) 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: > > > > > > > > > > > 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
