[DRBD-user] Fwd: Linstor User Guide Problem

[Gábor Hernádi]

Hello,

On Mon, Apr 18, 2022 at 3:08 AM Eric Robinson <eric.robinson at psmnv.com>
wrote:

> We noticed section 2.7 of the Linstor User Guide ends with the following
> statement, apparently intended for internal use:
>
>
>
> “FIXME describe how to route the controller <-> client communication
> through a specific netif.”
>
>
>
> Will that be fixed soon? It’s information we need to know.
>

Thank you for noting. We already removed the FIXME and will try to add that
information soon.

Besides the options you can use for defining the controller's IP address or
hostname (described in [1]), there is no way to tell the client through
which NIC it should reach the specified controller, using `linstor`
commands.
Please be aware that the client does not know about the configured "netif"s
specified through `linstor node interface ...` (sounds a bit hard having to
ask the controller on how to contact the very same controller :) )

What exactly are you trying to achieve here?

Does anyone here know if NIC assignment commands can be applied
> retroactively to resources that already exist? For example, if I issue the
> commands…
>
>
>
> linstor node interface create alpha 100G_nic 192.168.43.221
>
> linstor node interface create alpha 10G_nic 192.168.43.231
>
>
>
> linstor storage-pool set-property alpha pool_hdd PrefNic 10G_nic
>
> linstor storage-pool set-property alpha pool_ssd PrefNic 100G_nic
>
>
Yes that works, but it is not perfect right now. If you change the PrefNic
for a storage pool, all resources using that storage pool will update
accordingly but also simultaneously. That means that updating the PrefNic
on a diskless storage pool (for a diskless resource) will briefly
disconnect it from all diskful peers, which might cause some problems,
especially if that diskless resource is primary.


>
> …can I then modify existing resources that use the pool_hdd and pool_ssd
> storage pools and make them start using multiple paths?
>

Not sure if I understand this question correctly or not: If the question is
"can I move a resource from one storage pool to another", then the answer
is no. Only by deleting the resource and re-creating it into the new
storage pool and letting DRBD resync the data.
If you meant that question if you can configure DRBD to use multiple
network paths somehow, `PrefNic` is the wrong approach here. I just
realized that we are missing that part in our documentation, which we will
of course fix soon.
Until then, please feel free to explore the feature via the client's help
messages:
   linstor resource-connection path create -h


[1]
https://linbit.com/drbd-user-guide/linstor-guide-1_0-en/#s-using_the_linstor_client

-- 
Best regards,
Gabor Hernadi
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