Re: Adding multiple OSDs to existing cluster

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Hello,

On Wed, 17 Feb 2016 13:44:17 +0000 Ed Rowley wrote:

> On 17 February 2016 at 12:04, Christian Balzer <chibi@xxxxxxx> wrote:
> >
> > Hello,
> >
> > On Wed, 17 Feb 2016 11:18:40 +0000 Ed Rowley wrote:
> >
> >> Hi,
> >>
> >> We have been running Ceph in production for a few months and looking
> >> at our first big expansion. We are going to be adding 8 new OSDs
> >> across 3 hosts to our current cluster of 13 OSD across 5 hosts. We
> >> obviously want to minimize the amount of disruption this is going to
> >> cause but we are unsure about the impact on the crush map as we add
> >> each OSD.
> >>
> > So you are adding new hosts as well?
> >
> 
> Yes, we are adding 2 new hosts with 3 OSDs  and adding two drives/OSDs
> to an existing host
>
Nods.
 
> >> From the docs I can see that an OSD is added as 'in' and 'down' and
> >> wont get objects until the OSD service has started. But what happens
> >> to the crushmap while the OSD is 'down', is it recalculated? are
> >> objects misplaced and moved on the existing cluster?
> >>
> > Yes, even more so when adding hosts (well, the first OSD on a new
> > host).
> >
> > Find my "Storage node refurbishing, a  "freeze" OSD feature would be
> > nice" thread in the ML archives.
> >
> > Christian
> >
> 
> Thanks for the reference, the thread is useful,
> 
> I am right with the assumption that adding an OSD with:
> 
> [osd]
> osd_crush_initial_weight = 0
> 
Or by adding it with a weight of zero like this:

ceph osd crush add <osdnumber> 0 host=<osdhost>

> will not change the existing crush map
> 
Well it will change it (ceph osd tree will show it), but no data movement
will result from it, yes.

Christian
> 
> >> We think we would like to limit the rebuild of the crush map, is this
> >> possible or beneficial.
> >>
> >> Thanks,
> >>
> >> Ed Rowley
> >> _______________________________________________
> >> ceph-users mailing list
> >> ceph-users@xxxxxxxxxxxxxx
> >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> >>
> >
> >
> > --
> > Christian Balzer        Network/Systems Engineer
> > chibi@xxxxxxx           Global OnLine Japan/Rakuten Communications
> > http://www.gol.com/
> 
> Regards,
> 
> Ed Rowley
> 


-- 
Christian Balzer        Network/Systems Engineer                
chibi@xxxxxxx   	Global OnLine Japan/Rakuten Communications
http://www.gol.com/
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