I removed some osds from a host yesterday using the reweight method and it worked well. There was only one rebalance and then I could perform the rest of the documented removal steps immediately with no further recovery. I reweighted to 0.0.
Shinobu, can you explain why you have found 0.2 is better than 0.0? What happens when you use 0.2 and what happens when you use 0.0 ?
Rafael
On 12 January 2016 at 09:13, Shinobu Kinjo <skinjo@xxxxxxxxxx> wrote:
Based on my research, 0.2 is better than 0.0.
Probably it depends though.
> ceph osd crush reweight osd.X 0.0
Rgds,
Shinobu
----- Original Message -----
From: "Andy Allan" <gravitystorm@xxxxxxxxx>
To: "Rafael Lopez" <rafael.lopez@xxxxxxxxxx>
_______________________________________________Cc: ceph-users@xxxxxxxxxxxxxx
Sent: Monday, January 11, 2016 8:08:38 PM
Subject: Re: double rebalance when removing osd
On 11 January 2016 at 02:10, Rafael Lopez <rafael.lopez@xxxxxxxxxx> wrote:
> @Steve, even when you remove due to failing, have you noticed that the cluster rebalances twice using the documented steps? You may not if you don't wait for the initial recovery after 'ceph osd out'. If you do 'ceph osd out' and immediately 'ceph osd crush remove', RH support has told me that this effectively 'cancels' the original move triggered from 'ceph osd out' and starts permanently remapping... which still doesn't really explain why we have to do the ceph osd out in the first place..
This topic was last discussed in December - the documentation for
removing an OSD from the cluster is not helpful. Unfortunately it
doesn't look like anyone is going to fix the documentation.
http://comments.gmane.org/gmane.comp.file-systems.ceph.user/25627
Basically, when you want to remove an OSD, there's an alternative
sequence of commands that avoids the double-rebalance.
The better approach is to reweight the OSD to zero first, then wait
for the (one and only) rebalance, then mark out and remove. Here's
more details from the previous thread:
http://permalink.gmane.org/gmane.comp.file-systems.ceph.user/25629
Thanks,
Andy
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Senior Storage Engineer - Automation and Delivery
Infrastructure Services - eSolutions
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Monash University 3800
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Email rafael.lopez@xxxxxxxxxx
Infrastructure Services - eSolutions
738 Blackburn Rd, Clayton
Monash University 3800
Telephone: +61 3 9905 9118
Mobile: +61 4 27 682 670
Email rafael.lopez@xxxxxxxxxx
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