On 06/04/2018 05:54 PM, Clementine Hayat wrote: > Hi everybody! > > > I am starting this thread to discuss a new storage pool backend for > iSCSI using libiSCSI. > > There already is an iSCSI backend, however, it uses iscsiadm binary to > execute the desired operation. The binary can be spawned multiple > times during single execution of an API. This is suboptimal. > > Moreover the iscsi storage pool is mapped by the kernel into a block > device in /dev/. Iscsiadm makes operations directly on that block > device. Libiscsi on the other hand is sending the commands directly to > a remote iscsi portal. According to that, to be able to use a storage > pool using libiscsi we have to implement the storage pool backend > entirely. > > What we would have: > > Pool XML using iscsiadm: > > <pool type="iscsi" mode="host"> This sounds reasonable. However, I think for backwards compatibility we need to treat <pool type="iscsi"/> as mode="host". That is, if we don't parse any @mode, we must assume "host" and then we can format it into the XML back. > <name>virtimages</name> > <source> > <host name="iscsi.example.com"/> > <device path="iqn.2013-06.com.example:iscsi-pool"/> > <auth type='chap' username='myuser'> > <secret usage='libvirtiscsi'/> > </auth> > </source> > <target> > <path>/dev/disk/by-path</path> > </target> > </pool> > > Pool XML using libiscsi: > > <pool type="iscsi" mode="direct"> > <name>virtimages</name> > <source> > <host name="iscsi.example.com"/> > <device path="iqn.2013-06.com.example:iscsi-pool"/> > <auth type='chap' username='myuser'> > <secret usage='libvirtiscsi'/> > </auth> > </source> > </pool> > > The change that occurs is having a direct mode that will lead to the > libiscsi backend and the host mode that will lead to the actual > backend using iscsiadm. > > To tie the backend to the front was thinking about adding something > like VIR_STORAGE_POOL_LIBISCSI to storage_conf. Yes, that is one of the changes needed. Sounds right. > > About the domain XML only accept: > > <disk type='volume' device='disk'> > <driver name='qemu' type='raw'/> > <source pool='iscsi-pool' volume='unit:0:0:2' mode='direct'/> > <target dev='vdc' bus='virtio'/> > </disk> > > would be great using a switch case on VIR_STORAGE_POOL_LIBISCSI inside > domain_conf. > Yes. This is one of the places that need change. We tend to use typecasted switch()-es for exactly this reason - to help contributors identify places of interest when adding new type of something (not only storage pool). Michal -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
