[pve-devel] ceph replication speed

[Alexandre DERUMIER]

Hi,

my 2 cents, but is the crushmap ok ?
(are you sure that replication occur on osd on differents servers )


But indeed, replication is parallel, from first node to others node.
So it shouldn't slow down( of course, if hardware is same everywhere).

----- Mail original ----- 

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Eric Blevins" <eric at netwalk.com>, pve-devel at pve.proxmox.com 
Envoyé: Lundi 30 Décembre 2013 18:47:24 
Objet: Re: [pve-devel] ceph replication speed 

> size=3: 
> When you write to only three OSDs, each one replicates to two more OSDs, a 
> total of 9 OSD writes. 
> Half of the OSDs make two writes, I would expect reduced performance with 
> 50% of the OSDs doing twice the work. 

Thought a bit more about that, it does not really explain the slowdown. If all 6 OSD writes 
the overall throughput should be even better. 

Anyway, I will test that. 

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