Re: [PATCH v2] scsi: target: alua: do not report emtpy port group

[Dmitry Bogdanov <d.bogdanov@yadro.com>]

On Wed, Sep 14, 2022 at 02:18:40PM -0500, Mike Christie wrote:
> 
> On 9/12/22 4:45 PM, Dmitry Bogdanov wrote:
> >> Remember how ESX used to send a RTPG to one port and expect that it got
> >> every group and that the state info was all in sync (basically opposite
> >> if what's in the spec now)?
> >>
> >> The spec and ESX were updated, but I don't know if other OSs did this and
> >> if/when everyone was updated. Do you know this info? Are the old ESX versions
> >> that worked like that end of life?
> > ESXi is kinda a pain. But fortunately it has nothing to do with that
> > patch 😄
> 
> I didn't get why that is. How do you set up a distributed/cluster/HA target? I'm
> probably missing that part.
> 
> Software drivers like iscsi I get, but for HW drivers I didn't see how you do it.
> 
> For example, if you have 2 systems/nodes running LIO which each export the same
> device via 1 port each where one is active/optimized and the other is standby and you
> are using qla2xxx, then on the local node would you create 2 groups:
> 
> [root@ol8n4 alua]# pwd
> /sys/kernel/config/target/core/iblock_0/device0/alua
> 
> [root@ol8n4 alua]# ls
> default_tg_pt_gp  local  remote
> 
> Then under the mapped lun:
> 
> [root@ol8n4 lun_0]# pwd
> /sys/kernel/config/target/..../tpgt_1/lun/lun_0
> 
> in the alua_tg_pt_gp file you set that to local. That would then have tg_pt_gp_members
> set, but remote would not.
> 
> Before your patch, windows and ESX could do a RTPG to just one port/path and we would
> return the default, local and remote groups. We don't want the default group, but we
> wanted the local and remote one returned. With your patch we only return the the local
> one now. I wasn't sure how that works for drivers like qla2xxx.
> 
> For iscsi, you could just mirror the remote node locally, so you would have a second
> tpg:
> 
> [root@ol8n4 lun_0]# pwd
> /sys/kernel/config/target/..../tpgt_2/lun/lun_0
> 
> and in there set alua_tg_pt_gp to remote. Your patch works fine for that because both
> groups then have tg_pt_gp_members set so if the OS just does a RTPG to one path/port
> you get all the groups.
>
I use a virtual remote fabric driver to configure wwn/iqn-tpg-lun of
remote peers at each local node. In that way 'remote' alua port group
will have ports(RTPI) too. That allows RTPG (and other discovery-like
commands) report all ports in all port groups in the cluster.
I sent it within the RFC patchset:
https://patchwork.kernel.org/project/target-devel/patch/20220803162857.27770-36-d.bogdanov@yadro.com/

BR,
 Dmitry