Re: Worst thing that can happen if I have size= 2

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Adam;

I'd like to see that / those white papers.

I suspect what they're advocating is multiple OSD daemon processes per NVMe device.  This is something which can improve performance.  Though I've never done it, I believe you partition the device, and then create your OSD pointing at a partition.

Thank you,

Dominic L. Hilsbos, MBA 
Director - Information Technology 
Perform Air International Inc.
DHilsbos@xxxxxxxxxxxxxx 
www.PerformAir.com

-----Original Message-----
From: Adam Boyhan [mailto:adamb@xxxxxxxxxx] 
Sent: Wednesday, February 3, 2021 8:50 AM
To: Magnus HAGDORN
Cc: ceph-users
Subject:  Re: Worst thing that can happen if I have size= 2

Isn't this somewhat reliant on the OSD type? 

Redhat/Micron/Samsung/Supermicro have all put out white papers backing the idea of 2 copies on NVMe's as safe for production. 


From: "Magnus HAGDORN" <Magnus.Hagdorn@xxxxxxxx> 
To: pseudo@xxxxxxxxxxxxx 
Cc: "ceph-users" <ceph-users@xxxxxxx> 
Sent: Wednesday, February 3, 2021 4:43:08 AM 
Subject:  Re: Worst thing that can happen if I have size= 2 

On Wed, 2021-02-03 at 09:39 +0000, Max Krasilnikov wrote: 
> > if a OSD becomes unavailble (broken disk, rebooting server) then 
> > all 
> > I/O to the PGs stored on that OSD will block until replication 
> > level of 
> > 2 is reached again. So, for a highly available cluster you need a 
> > replication level of 3 
> 
> 
> AFAIK, with min_size 1 it is possible to write even to only active 
> OSD serving 
> 
yes, that's correct but then you seriously risk trashing your data 

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