Re: [SPDK] Namespace sharing between multiple controller

[Walker, Benjamin <benjamin.walker at intel.com>]

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On Wed, 2017-03-08 at 23:42 +0530, Ankur Srivastava wrote:
> Hi All,
> 
> I am using null block devices on my Target side and here is my conf
> file snap (app/nvmf_tgt/nvmf_tgt -c etc/spdk/nvmf.conf.in)
> 
> [Subsystem1]
>   NQN nqn.2016-06.io.spdk:cnode1
>   Core 0
>   Mode Virtual
>   Listen RDMA 192.168.25.3:4420
>   SN SPDK00000000000001
>   Namespace Malloc0
> 
> [Subsystem2]
>   NQN nqn.2016-06.io.spdk:cnode2
>   Core 1
>   Mode Virtual
>   Listen RDMA 192.168.25.31:4420
>   SN SPDK00000000000001
>   Namespace Malloc1
> 
> 
> How can I create multiple controllers and how can I share namespace
> like(Malloc0, Malloc1) between different controllers ??

A new controller will be created each time a new NVMe-oF host
(initiator) connects to a subsystem. That controller will be able to
see all of the namespaces within a subsystem. Note that we don't
currently have emulation for NVMe reservations, so coordination will
need to be done by the clients.

So if you want to have a subsystem with two shared namespaces and two
clients connected, just write:

[Subsystem1]
  NQN nqn.2016-06.io.spdk:cnode1
  Core 0
  Mode Virtual
  Listen RDMA 192.168.25.3:4420
  SN SPDK0000000000001
  Namespace Malloc0
  Namespace Malloc1

Start up the target with that config and then connect two clients to
the same subsystem. They'll each see their own controller but share
namespaces.

The best way to think about NVMe controllers in NVMe-oF is that they're
just sessions in the networking sense of the word. We even call them
spdk_nvmf_session in our code, as opposed to spdk_nvmf_controller. This
isn't an implementation choice that SPDK is making either - that's
really the intended meaning of a controller in the NVMe-oF
specification which sometimes refers to them as "controller sessions".

> 
> 
> Regards
> Ankur
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> SPDK(a)lists.01.org
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