large number of hot plug disks

[Daniel P. Berrangé]

On Tue, Sep 08, 2020 at 08:19:21AM -0400, Alexander Wels wrote:
> Hi,
> 
> I am working on a project, and one of the requirements is that I can
> hotplug a large number of disks. Think several dozens to potentially 100+.
> The guest OS will be some linux flavor so it should have no problem with a
> large number of disks.
> 
> During my experimentation I quickly ran into the "No available PCI slots"
> limit. I found https://libvirt.org/pci-hotplug.html explaining to me why
> the limit is there. Now I could add a bunch of pcie-root-ports ahead of
> time, but there is likely a limit to that as well. So before I go down some
> crazy paths, I figured I would ask on here if there is a better plan than
> adding a bunch of root ports for adding a large number of hotplugged disks?

While you can add extra PCI bridges, I'd suggest using virtio-scsi
instead

These blog posts should serve as warning about some of the limits
you'll hit:

https://rwmj.wordpress.com/2017/04/25/how-many-disks-can-you-add-to-a-virtual-linux-machine/
https://rwmj.wordpress.com/2017/04/28/how-many-disks-can-you-add-to-a-virtual-linux-machine-contd/

Regards,
Daniel
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