[RFC PATCH] nvmet: Back namespace with files

[Hannes Reinecke]

On 03/13/2017 05:11 PM, Keith Busch wrote:
> On Mon, Mar 13, 2017 at 10:32:38AM +0200, Sagi Grimberg wrote:
>>> Hm, implementation details aside for a second, isn't namespace management
>>> more useful on fabrics than pci? It's like managing LUNs on a SAN,
>>> but with spec defined commands.
>>
>> Not exactly, usually namespace/lun provisioning is something that a
>> given host does not typically do or even aware of. Unlike in PCIe,
>> in fabrics, the host does not really own "the" subsystem, it just owns
>> a virtual subsystem that the target exposed for it.
>>
>> If we do support namespace management in the linux target, it'd need
>> to be emulated somehow, obviously a host cannot simply add
>> unprovisioned resources.
> 
> Yes, the RFC was light on details, and I'm probably getting ahead of
> myself with the file-as-a-namespaces suggestion.
> 
> I'd like an NVMe subsystem to be provided a pool of storage that it
> may dynamically carve into namespaces and attach to connected hosts as
> needed. I also want hosts to do this using the spec defined Namespace
> Management commands. That isn't all that unusual from what I hear.
> 
> This doesn't really require a filesystem. Maybe LVM is more appropriate,
> but I think that'd require userspace to manage the LVs. Still, file backed
> namespaces has uses if only for testing purposes, like LIO's FILEIO.
> 
I'm not against this in principle, but can we make the selectable?
IE not ripping out the original implementation, but rather have them
both side-by-side and let the admin decide what he wants to use?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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