[SPDK] Re: Spdk nvme CLI - block device

Hi
Thanks for your reply..
The goal is to have an initiator in user space which connects to nvmf target and exposes block devices in the host(initiator) machine.
Same way nvme-cli does it... But without the Linux kernel driver in the initiator.
The last limitation derives from the fact that not all customer would move to a kernel which supports tcp nvmf

Thanks
-gili
________________________________
From: Zawadzki, Tomasz <tomasz.zawadzki(a)intel.com>
Sent: Monday, April 6, 2020 6:14:42 PM
To: Storage Performance Development Kit <spdk(a)lists.01.org>
Subject: [SPDK] Re: Spdk nvme CLI - block device

Hello Gili,

If I understand correctly the goal is to prepare data on a bdev before exposing it via NVMe-oF (or other targets - vhost/iSCSI) ?

One way would be to connect to SPDK target with kernel initiator - even locally within single machine.
Then perform necessary preparation using already available tooling.
As you've noted it is possible to create device in kernel from bdev using NBD as well.

Please see https://spdk.io/doc/bdev.html and appropriate target documentation to help with set of RPCs that might help.

Note:
nvme CLI is not needed to configure SPDK target or SPDK initiator, this can be done via RPC.
Branch spdk-1.6 for nvme CLI was created to interact with NVMe bdevs in SPDK. Which since has been improved to work
with stock nvme CLI when using https://spdk.io/doc/bdev.html#bdev_config_nvme_cuse

Thanks,
Tomek

> -----Original Message-----
> From: Gili Buzaglo <Gili.Buzaglo(a)kioxia.com>
> Sent: Saturday, April 4, 2020 11:59 AM
> To: spdk(a)lists.01.org
> Subject: [SPDK] Spdk nvme CLI - block device
>
> Hi
> I tried to understand if nvme CLI based on spdk-1.6 can somehow generate a
> block device without using the nvme fabrics kernel module.
> I managed to add tcp support and connect ,but then the code goes to the
> kernel module and no block device was added.
> In general , I know that it is possible to create block devices which are
> implemented in user space (for example with nbd) .. and I know spdk has
> block device layer..
> Does someone think that what I did is somehow possible ?
>
> The motivation for this is easy host installation without the requirement to
> replace kernel or application changes.
> I'm aware there will be a performance impact..
>
> Thanks
> -gili
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