How does NVMe/FC namespace support two different OS platform to perform LANfree backup

[yihui]

Here is one issue from my customer who using the NVMe/ FC with LANfree backup requirement: 

Environment info:
Storage system : NetApp A250
ONTAP version: 9.10.1
Storage  Protocol： NVMe over FC

Five VMware ESxi host: vSphere 7.0

One Redhat Linux version  8.2 (4.18.0-193.el8.x86_64 ) with Veritas NBU Backup Server with Emulex LPe31002 HBA, driver: 12.8.x.x

Topology:

Issue:
All of the ESXi host can  read/write the nvme datastore except the Linux backup server . 

Does ONTAP support mapping single nvme namespace to different OS platform (VMware and Redhat) ?
or
How to achieve  LANfree backup on NVMe/FC protocol with  VMware ESXi cluster  and Linux Backup Server ? 

it doesn’t seem to work, because  I found some from reminder from ONTAP online guide  as below: 

[Ontapforrum]

I found the following text in this article: "It should be mentioned that the current NVMe specification does not specify namespace share across NVM subsystem, which is settled down in NVMe 1.4 draft specification."

https://nvmexpress.org/nvme-over-fabrics-part-two/

I am not sure if that corresponds to the issue/concern you have raised.   When you say it doesn't seem to work, does it not allow you to add the additional Host or it (volume) does not get detected by the Linux host. 

Anyway, you are lucky to get hands on with this new Protocol based technology. Please do share your experience

Just curious to know : How are you planning to backup the NVMe backed VMware resources from the Linux server: Do you have any 3rd party backup software ?

[jaikumar]

Yes Namespace can be shared across 2 different Host OS but the host nqn must be part of the same subsystem. say ,  Subsystem-1 can have nqn-1 of host os 1 and nqn-2 of host os-2 , NameSpace-1 mapped to Subsystem-1. And Namespace-1 can be seen on both the host os.

Now can constituent of the subsystem can be nqn of 2 different host os flavour ?
There isn't any explicit mention in the spec that subsystem must always constitute nqn from the same host operating system. 

And when it comes to NetApp , when a subsystem is created , host os of the constituent host nqn (part of subsystem) must be specified

example,

vserver nvme subsystem create -vserver netapp_vserver -subsystem ss -ostype  [ linux vmware windows ]

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