Re: [Qemu-block] [Qemu-devel] [PATCH v5 3/4] qmp: add monitor command to add/remove a child

[Alberto Garcia]

On Thu 08 Oct 2015 08:15:25 AM CEST, Markus Armbruster wrote:
>> For the second point, you should also consider how useful this
>> feature is to management tools. Just being able to remove and attach
>> children from a quorum node seems very useful on its own. I don't see
>> why we should wait for having support for other block drivers; also,
>> for most block drivers there is no meaningful way of adding or
>> removing children as nicely as that is possible for quorum.
>
> Okay, this is an argument I might be able to buy.

Note that if we want to make this interface stable there's one use case
missing: there's currently no way to change the vote threshold.

This is maybe not so important for the COLO use case, but for the
general case of adding and removing children from a quorum node having
the possibility to change the threshold makes a lot of sense.

That would probably require a its own API ('quorum-set-threshold' or
something like that) so I don't think it has an effect on these
child-add and child-del commands, but I wanted to mention it here anyway
in case someone sees something that I'm overlooking.

Berto