[dm-devel] [PATCH] multipath-tools: convert back HUAWEI/XSG1 to multibus

[Martin Wilck]

On Fri, 2021-03-26 at 04:08 +0100, Xose Vazquez Perez wrote:
> This reverts commit ad206af1716437e84bbd81de6c4da7961d9a41d2
> 
> Recommended configs are, info from:
> - RHEL 
> https://download.huawei.com/edownload/e/download.do?actionFlag=download&nid=EDOC1100113070&partNo=6001&mid=SUPE_DOC&_t=1612885511000
> - SLES 
> https://download.huawei.com/edownload/e/download.do?actionFlag=download&nid=EDOC1100117892&partNo=6001&mid=SUPE_DOC&_t=1612885538000
> 
> - without HyperMetro:
> vendor "HUAWEI"
> product "XSG1"
> path_grouping_policy multibus
> no_path_retry 15
> 
> - with HyperMetro:
> vendor "HUAWEI"
> product "XSG1"
> path_grouping_policy group_by_prio
> prio alua
> failback immediate
> no_path_retry 15
> 
> ALUA is only used with HyperMetro(cluster of two arrays).
> 
> Cc: Zhouweigang (Jack) <zhouweigang09 at huawei.com>
> Cc: Zou Ming <zouming.zouming at huawei.com>
> Cc: Benjamin Marzinski <bmarzins at redhat.com>
> Cc: Martin Wilck <mwilck at suse.com>
> Cc: Christophe Varoqui <christophe.varoqui at opensvc.com>
> Cc: DM-DEVEL ML <dm-devel at redhat.com>
> Signed-off-by: Xose Vazquez Perez <xose.vazquez at gmail.com>

Forgive me if I'm missing something here, but what is this good for?
multipathd detects ALUA support by default.

 1 if the device doesn't support ALUA, it falls back to "const" anyway,
   in which case "group_by_prio" degenerates to "multibus" - which is
   exactly what this patch does;
 2 if the device supports ALUA, but returns the same ALUA state for
   all ports, again "group_by_prio" degenerates to "multibus";
 3 if the device supports ALUA and returns different states for 
   different ports, "group_by_prio" is the best bet anyway.

So why not just use "group_by_prio"?

Martin