replicas in ceph storage

replicas in ceph storage

[udit agarwal]

Hi,
 I have a query regarding the way to determine the no. of replicas that are
created for each object in the ceph storage system. I couldn't find a way to
determine this. please help me with this.

 Thanks in advance.

--Udit Agarwal

Re: replicas in ceph storage

[Wido den Hollander]

Hi,

On 06/06/2012 12:24 PM, udit agarwal wrote:
> Hi,
>   I have a query regarding the way to determine the no. of replicas that are
> created for each object in the ceph storage system. I couldn't find a way to
> determine this. please help me with this.
>

The number of replicas is set by the "rep size" attribute of the pool 
you are storing the object in.

$ ceph osd dump -o -|grep "rep size"

That will show something like:

pool 0 'data' rep size 3 crush_ruleset 0 object_hash rjenkins pg_num 
2560 pgp_num 2560 lpg_num 2 lpgp_num 2 last_change 91 owner 0 
crash_replay_interval 45
pool 1 'metadata' rep size 3 crush_ruleset 1 object_hash rjenkins pg_num 
2560 pgp_num 2560 lpg_num 2 lpgp_num 2 last_change 90 owner 0
pool 2 'rbd' rep size 3 crush_ruleset 2 object_hash rjenkins pg_num 2560 
pgp_num 2560 lpg_num 2 lpgp_num 2 last_change 630 owner 0
	removed_snaps [1~1]

In this case all the pools have a "size" of 3, which means all objects 
stored in these pools will be replicated three times.

You can change this parameter with:

$ ceph osd pool set <pool> size <size>

Wido

>   Thanks in advance.
>
> --Udit Agarwal
>
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