Re: OSD replacement feature

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That is correct. The goal is to only refill the replacement OSD disk. Otherwise, if the OSD is only down for less than mon_osd_down_out_interval (5 min default) or noout is set, no other data movement would occur.

David

On 11/23/15 8:45 PM, Wei-Chung Cheng wrote:
2015-11-21 1:54 GMT+08:00 David Zafman <dzafman@xxxxxxxxxx>:
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.
Hi David,

It good to without causing any data movement when we want to replaced
failure osd.

But I don't have any idea to complete it, could you give some opinions?

I though if we want to replace failure we must move the object data on
failure osd to new(replacement) osd?

Or I got some misunderstanding?

thanks!!!
vicente

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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