Hi Jason, Thanks for the detailed write-up... On Wed, 11 Oct 2017 08:57:46 -0400, Jason Dillaman wrote: > On Wed, Oct 11, 2017 at 6:38 AM, Jorge Pinilla López <jorpilo@xxxxxxxxx> > wrote: > > > As far as I am able to understand there are 2 ways of setting iscsi for > > ceph > > > > 1- using kernel (lrbd) only able on SUSE, CentOS, fedora... > > > > The target_core_rbd approach is only utilized by SUSE (and its derivatives > like PetaSAN) as far as I know. This was the initial approach for Red > Hat-derived kernels as well until the upstream kernel maintainers indicated > that they really do not want a specialized target backend for just krbd. > The next attempt was to re-use the existing target_core_iblock to interface > with krbd via the kernel's block layer, but that hit similar upstream walls > trying to get support for SCSI command passthrough to the block layer. > > > > 2- using userspace (tcmu , ceph-iscsi-conf, ceph-iscsi-cli) > > > > The TCMU approach is what upstream and Red Hat-derived kernels will support > going forward. SUSE is also in the process of migrating to the upstream tcmu approach, for the reasons that you gave in (1). ... > The TCMU approach also does not currently support SCSI persistent > reservation groups (needed for Windows clustering) because that support > isn't available in the upstream kernel. The SUSE kernel has an approach > that utilizes two round-trips to the OSDs for each IO to simulate PGR > support. Earlier this summer I believe SUSE started to look into how to get > generic PGR support merged into the upstream kernel using corosync/dlm to > synchronize the states between multiple nodes in the target. I am not sure > of the current state of that work, but it would benefit all LIO targets > when complete. Zhu Lingshan (cc'ed) worked on a prototype for tcmu PR support. IIUC, whether DLM or the underlying Ceph cluster gets used for PR state storage is still under consideration. Cheers, David _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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