[pve-devel] Migration of VM/Container on custom storage type

[pve-devel] Migration of VM/Container on custom storage type

[Max Schettler via pve-devel]

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From: Max Schettler <max@simplyblock.io>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
Subject: Migration of VM/Container on custom storage type
Date: Tue, 15 Apr 2025 11:55:28 +0200
Message-ID: <48b4f31c-c8dd-44bf-9dc3-3dd478b3bb08@simplyblock.io>

Hi,

I'm developing a Proxmox storage plugin. Trying to use the 
high-availability features or migrating VMs/Containers to another 
hypervisor in the cluster I get error messages about the storage type 
I'm providing not being supported.

Looking at the source, it seems like there is a whitelist of 
storagetypes, and no feature check like e.g. for snapshotting. Am I 
right to assume there is currently no way of providing a storage backend 
that can use this functionality? Are there details beyond this check 
that prevent this possibility?

If I am reading the code correctly, are there plans to extend the Plugin 
API s.t. it becomes an option? Providing this feature would be an 
important addition to our plugin.

Thanks in advance &
kind regards
Max



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Re: [pve-devel] Migration of VM/Container on custom storage type

[Fabian Grünbichler]

> Max Schettler via pve-devel <pve-devel@lists.proxmox.com> hat am 15.04.2025 11:55 CEST geschrieben:
> Hi,
> 
> I'm developing a Proxmox storage plugin. Trying to use the 
> high-availability features or migrating VMs/Containers to another 
> hypervisor in the cluster I get error messages about the storage type 
> I'm providing not being supported.

Hi! thanks for reaching out!

out of interest, what is the storage plugin for?

in general it always helps to provide a bit of detail and to include all
error messages. I made an educated guess below what your issue is, if it
is not correct, please just add more details and I am sure we can figure
it out.

> Looking at the source, it seems like there is a whitelist of 
> storagetypes, and no feature check like e.g. for snapshotting. Am I 
> right to assume there is currently no way of providing a storage backend 
> that can use this functionality? Are there details beyond this check 
> that prevent this possibility?

at the moment there is a list of shared storage types in PVE::Storage::Plugin
that is used to set the shared flag on the storage instance (which in turn
makes migrations ignore volumes there since a storage being shared means its
volumes have identical content on all nodes where the storage is available).

the only option at the moment is to add your type to that list (it is shared
state across all plugins, so any plugin can do so).

> If I am reading the code correctly, are there plans to extend the Plugin 
> API s.t. it becomes an option? Providing this feature would be an 
> important addition to our plugin.

I think we will switch to just making this a property of the plugin in a
declarative fashion as part of revamping the plugin interface, but that has
not happened yet, so for now the only option to add a new shared plugin is
to push to that list.

you might be interested Max (still open/iterated upon) series documenting
and improving the plugin interface:

https://lore.proxmox.com/pve-devel/20250326142059.261938-1-m.carrara@proxmox.com/

while some parts are still in flux there, it should give some missing details!

Fabian


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