when to use "/dev/nvme0ns1"

[Krishnamraju Eraparaju]

Thank you Warner Losh & Yuri Pankov.

Can I use nvmeXnsY for IO?
Looks like fio shows better performance with nvmeXnsY, then nvd/nda devices.

Thanks,
ekraju.

On Sun, Dec 6, 2020 at 11:13 AM Warner Losh <imp at bsdimp.com> wrote:

>
>
> On Sat, Dec 5, 2020 at 10:36 PM Yuri Pankov <yuripv at yuripv.dev> wrote:
>
>> Krishnamraju Eraparaju wrote:
>> > Hi All,
>> >
>> >
>> > I see there are two ways of accessing NVMe disk:
>> >     1)GEOM based: /dev/nvd0 or /dev/nda0
>> >     2)/dev/nvme0ns1
>> >
>> > When should one use " /dev/nvme0ns1"?
>>
>> See nvmecontrol(8) for the commands that operate on namespace ids.  And
>> while you could still use nvd/nda devices for those, specifying the
>> namespace explicitly could be helpful.
>>
>> An excerpt from man page:
>>
>> DEVICE NAMES
>>       Where ⟨namespace-id⟩ is required, you can use either the nvmeXnsY
>>       device, or the disk device such as ndaZ or nvdZ.  The leading /dev/
>>       is omitted.
>>
>
> Yes. nvd* and nda* are block devices. nvme0ns1 is for administrative
> things when you may or may not have an nda/nvd device hanging around, or
> you want to deal with a specific thing and don't know the mapping to the
> nda/nvd device.
>
> Warner
>