It was required for Bobtail to Cuttlefish and Cuttlefish to Dumpling.  

Exactly how many mons do you have such that you are concerned about failure?  
If you have let’s say 3 mons, you update all the bits, then it shouldn’t take 
you more than 2 minutes to restart the mons one by one.  You can take your time 
updating/restarting the osd’s.  I generally consider it bad practice to save 
your system updates for a major ceph upgrade. How exactly can you parse the 
difference between a ceph bug and a kernel regression if you do them all at 
once?  You have a resilient system why wouldn’t you take advantage of that 
property to change one thing at a time?  So what we are really talking about 
here is a hardware failure in the short period it takes to restart mon services 
because you shouldn’t be rebooting.  If the ceph mon doesn’t come back from a 
restart then you have a bug which in all likelihood will happen on the first 
mon and at that point you have options to roll back or run with degraded mons 
until Sage et al puts out a fix.  My only significant downtime was due to a bug 
in a new release having to do with pg splitting, 8 hours later I had my fix.

> On Jul 14, 2017, at 10:39 AM, Lars Marowsky-Bree <l...@suse.com> wrote:
> 
> On 2017-07-14T10:34:35, Mike Lowe <j.michael.l...@gmail.com> wrote:
> 
>> Having run ceph clusters in production for the past six years and upgrading 
>> from every stable release starting with argonaut to the next, I can honestly 
>> say being careful about order of operations has not been a problem.
> 
> This requirement did not exist as a mandatory one for previous releases.
> 
> The problem is not the sunshine-all-is-good path. It's about what to do
> in case of failures during the upgrade process.
> 
> 
> 
> -- 
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 
> 21284 (AG Nürnberg)
> "Experience is the name everyone gives to their mistakes." -- Oscar Wilde
> 

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