Facing errors while creating Multipath-Raid using mdadm

[utnoor]

Hi Natasha3,

Kindly follow the link & re-create the iSCSI LUNs as per the document however,

my suggestion would be to use multipath rather than madam (not as advanced as multipath)

[Natasha3]

 I tried re-creating LUNS as suggested by the document by making use of multipath instead of mdadm. But facing same errors. After receiving the ISCSI devices on my initator server , wwids/wwn of the devices changes making it difficult to make multipath on them.   

[utnoor]

Hi Natasha3,

If it works it can be used otherwise, it is better to use multipath rather than mdadm because , as we told earlier the module will not be loaded by default to support software RAID with multipath "MD_MULTIPATH provides a simple multi-path personality for use the MD framework. It is not under active development. New projects should consider using DM_MULTIPATH which has more features and more testing" 

To create the software RAID with multipath.........we require "md_multipath" module which is not available to load in RHEL 8.7 by default.......

The concerned information code is given in the below link............https://elixir.bootlin.com/linux/v3.8/source/drivers/md/multipath.c

[Natasha3]

Hey @utnoor ,
Tried all your suggestions.  Also used "DM_MULTIPATH" but I am unable to create multipath of my iscsi devices. 
The problem I am facing is that,
My iscsi devices (which is same physical devices sent via different paths to a server) are having different serial number, wwid, wwn number , iscsi id on the server when transferred to the server via two different controllers . 
Therefore whenever I try to make multipath them using "DM_MULTIPATH" i get error saying 
"only one orphaned path". It is not recognising other path (another iscsi device which is same physical device). 

[utnoor]

Hi Natasha3,

Please follow the link provided earlier to flush the multipath & re-create the maps to the LUNs

If any issues then it has to be checked at iSCSI end.

https://www.qsan.com/data/dl_files/qs_wp_iSCSI-MPIO-in-Linux%20(en).pdf    

[Natasha3]

@utnoor 

Hey Utnoor,

Checked this code.  
https://elixir.bootlin.com/linux/v3.19.8/source/drivers/md/multipath.c

Is this code under developement ? Is thiis code working? Can it solve our problems related to logical disks persisent naming of unique identifiers incase multipath?