And that is why I thought to respond.  I was hoping for a little more
specifics about what that daemon was going to do.  Thank's Gregory, I'm
really excited for it!

On Wed, Jun 14, 2017 at 11:05 AM Gregory Farnum <[email protected]> wrote:

> On Wed, Jun 14, 2017 at 7:52 AM David Turner <[email protected]>
> wrote:
>
>> In the Firefly release of Ceph, all OSDs asked the mons every question
>> about maps that they had.  In the Jewel release, that burden was taken off
>> of the Mons and given to the OSDs as often as possible to ask each other.
>> This was done because the Mons were found to be a bottleneck for growing a
>> cluster very large.  I had a cluster on Firefly that the mons couldn't
>> handle the load if the cluster grew larger than 1200 OSDs.  Now in Luminous
>> they are again removing some strain on the Mon daemons to allow clusters to
>> continue to grow to a larger scale.  Like John mentioned, this new daemon
>> is there to remove strain on the Mons.
>>
>> "It is not mandatory to place mgr daemons on the same nodes as mons, but
>> it is almost always sensible."
>>
>> This quote from John's PR for the ceph documentation shows that this is
>> not a change for standard Ceph usage, but for extreme clusters pushing the
>> bounds of how large you can grow a cluster.  Few times will anyone need to
>> get that much more performance from their mons, but it is awesome that they
>> have created this new daemon to be able to isolate these tasks when you do
>> need it for scale.
>>
>
> While we're mostly starting with tasks around scale, that's definitely not
> the only reason for the manager. There's already a prototype web dashboard
> that lets you see the state of things integrated into the manager; it's
> gathering the "perfcounters" statistics that have previously only been
> accessible via a daemon's admin socket; we're adding more complicated kinds
> of CRUSH reweighting and balancing via the manager that should help balance
> out cluster utilization. All these things would have been much more
> difficult in the monitor and will help small clusters as well. :)
> -Greg
>
>
>>
>> On Wed, Jun 14, 2017 at 10:29 AM John Spray <[email protected]> wrote:
>>
>>> On Wed, Jun 14, 2017 at 6:47 AM, Manuel Lausch <[email protected]>
>>> wrote:
>>> > Hi,
>>> >
>>> > we decided to test a bit the upcoming ceph release (luminous). It seems
>>> > that I need to install this ceph-mgr daemon as well. But I don't
>>> > understand exactly why I need this service and what I can do with it.
>>> >
>>> > The ceph Cluster is working well without installing any manager daemon.
>>> > However in the ceph status output there is a health error ("no active
>>> > mgr")
>>> >
>>> > My questions:
>>> > Can we run the cluster without this additional daemon? If yes, is it
>>> > possible to supress this health error?
>>>
>>> You do need the daemon -- in luminous, it is responsible for
>>> populating parts of the health monitoring, especially the status of
>>> PGs.
>>>
>>> > What exactly is the purpose of this service. The documentation
>>> oncontains
>>> > very rare information about it.
>>>
>>> You probably already found the existing doc page for mgr:
>>> "The Ceph Manager daemon (ceph-mgr) runs alongside monitor daemons, to
>>> provide additional monitoring and interfaces to external monitoring
>>> and management systems."
>>>
>>> I've fleshed it out a little bit:
>>> https://github.com/ceph/ceph/pull/15690
>>>
>>> John
>>>
>>> >
>>> >
>>> > Regards
>>> > Manuel
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > --
>>> > Manuel Lausch
>>> >
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