Re: How does monitor know OSD is dead?

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On Sun, 30 Jun 2019, Bryan Henderson wrote:
> > I'm not sure why the monitor did not mark it _out_ after 600 seconds
> > (default)
> 
> Well, that part I understand.  The monitor didn't mark the OSD out because the
> monitor still considered the OSD up.  No reason to mark an up OSD out.
> 
> I think the monitor should have marked the OSD down upon not hearing from it
> for 15 minutes ("mon osd report interval"), then out 10 minutes after that
> ("mon osd down out interval").

Yes--if it didn't, that a bug.  Any logs would be helpful.

I'm a bit confused about what happened here, though: that 600 second 
interval is only important if *every* OSD in the system is down.  If you 
reboot the data center, why didn't *any* OSD daemons start?  (And even if 
none did, having the ceph -s report all OSDs down instead of up isn't 
going to change anything except whether your pager is going off, right?)

sage

 > 
> And that's worst case.  Though details of how OSDs watch each other are vague,
> I suspect an existing OSD was supposed to detect the dead OSDs and report that
> to the monitor, which would believe it within about a minute and mark the OSDs
> down.  ("osd heartbeat interval", "mon osd min down reports", "mon osd min down
> reporters", "osd reporter subtree level").
> 
> -- 
> Bryan Henderson                                   San Jose, California
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> 
> 
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