[DRBD-user] Fwd: Linstor User Guide Problem

[Eric Robinson]

Hi Gabor,

To answer your question, “What are you trying to achieve?” …

Our DB clusters have 4 NICS in 2 bonds. There is a “front” bond attached to the client-facing network, plus a “back” bond attached to the replication network. Currently, DRBD is configured on all nodes to use the IP addresses associated with the back bonds. We have almost 400 resources already up and running. I recently learned that DRBD can be configured to use multiple network paths in an active/standby fashion. I want to enable a secondary path using the front bonds. I’m looking for the easier and most reliable way to accomplish that, so if something happens to the replication network, DRBD will seamlessly transition to using the front network.


From: drbd-user-bounces at lists.linbit.com <drbd-user-bounces at lists.linbit.com> On Behalf Of Gábor Hernádi
Sent: Tuesday, April 19, 2022 8:27 AM
To: drbd-user <drbd-user at lists.linbit.com>
Subject: [DRBD-user] Fwd: Linstor User Guide Problem

Hello,

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