Hi ceph users, 

Ceph have a very good documentation about technical usage, but there is a lot 
of conceptual things missing (from my point of view) 
It's not easy to understand all at the same time, but yes, little by little 
it's working. 

Here are some questions about ceph , hope someone can take a little time to 
point me where I can find answers : 

- Backup : 
Do you backup data from a CEPH cluster or you consider a copy as a backup of 
that file ? 
Let's say I have replica size of 3 . Somehow , my crush map will keep 2 copy in 
my main rack and 1 copy to another rack in another datacenter 
Can I consider the third copy as a backup ? What would be your position ? 

- Writing process of ceph object storage using radosgw 
Simple question, but not sure about it. 
The more replica the more slower will be my cluster ? Does CEPH have to 
acknowledge the number of replica before saying it's good ? 
>From what I read, CEPH will write and acknowledge the de primary OSD of the 
>pool , So if that the cas, I does not matter how many replica I want and how 
>far are situated the others OSD that would work the same. 
Can I chose myseft the primary OSD in my zone 1 , have a copy on zone 2 (same 
rack) and a third zone 3 in another datacenter that might have some latency . 

- Data persistance / availability 
If crush map is by hosts and I have 3 hosts with replication of 3 
This means , I will have 1 copy on each hosts 
Does it means I can lost 2 hosts and still have my cluster working, at least on 
read mode ? and eventually in write too if i say , osd pool default min size = 
1 

Thanks for your help. 
- 

BenoƮt G 
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