[ceph-users] New OSD with weight 0, rebalance still happen...

Marco Gaiarin gaio at sv.lnf.it
Thu Nov 22 00:22:03 PST 2018

Ceph still surprise me, when i'm sure i've fully understood it,
something 'strange' (to my knowledge) happen.

I need to move out a server of my ceph hammer cluster (3 nodes, 4 OSD
per node), and for some reasons i cannot simply move disks.
So i've added a new node, and yesterday i've setup the new 4 OSD.
In my mind i will add 4 OSD with weight 0, and then slowly i will lower
the old OSD weight and increase the weight of the new.

I've done before:

	ceph osd set noin

and then added OSD, and (as expected) new OSD start with weight 0.

But, despite of the fact that weight is zero, rebalance happen, and
using percentage of rebalance 'weighted' to the size of new disk (eg,
i've had 18TB circa of space, i've added a 2TB disks and roughly 10% of
data start to rebalance).

Why? Thanks.

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