There are two reasons for having a ceph-disk replace feature.
1. To simplify the steps required to replace a disk
2. To allow a disk to be replaced proactively without causing any data
movement.
So keeping the osd id the same is required and is what motivated the
feature for me.
David
On 11/20/15 3:38 AM, Sage Weil wrote:
On Fri, 20 Nov 2015, Wei-Chung Cheng wrote:
Hi Loic and cephers,
Sure, I have time to help (comment) on this feature replace a disk.
This is a useful feature to handle disk failure :p
An simple step is described on http://tracker.ceph.com/issues/13732 :
1. set noout flag - if the broken osd is primary osd, could we handle well?
2. stop osd daemon and we need to wait the osd actually down. (or
maybe use deactivate option with ceph-disk)
these two above step seems OK.
about handle crush map, should we remove the broken osd out?
If we do that, why we set noout flag? It still trigger re-balance
after we remove osd from crushmap.
Right--I think you generally want to do either one or the other:
1) mark osd out, leave failed disk in place. or, replace with new disk
that re-uses the same osd id.
or,
2) remove osd from crush map. replace with new disk (which gets new osd
id).
I think re-using the osd id is awkward currently, so doing 1 and replacing
the disk ends up moving data twice.
sage
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