On 06/05/2018 10:14 AM, Jiri Denemark wrote: > On Tue, Jun 05, 2018 at 09:37:06 +0200, Michal Privoznik wrote: >> 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. > > Thanks a lot for working on this, I'm looking forward to switching to > the new pool. > >>> 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. > > On the other hand, we could perhaps just introduce a new pool type, > something like > > <pool type='iscsi-direct'>...</pool> > > which would match with VIR_STORAGE_POOL_ISCSI_DIRECT and avoid the black > magic of translating type="iscsi" to VIR_STORAGE_POOL_LIBISCSI or > VIR_STORAGE_POOL_ISCSI depending on the mode attribute. Not to mention > that old libvirt would just completely ignore the mode attribute, but it > would complain about unknown pool type. I don't see much problem with old libvirt ignoring @mode attribute. Storage pools are not something we migrate back and forth like domains. Sure, there's always the case of downgrading libvirt, but, that means being forward compatible actually. I mean, any new element we add to XML is not parsed by older libvirt. Michal -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
