Whether read I/O is accpted when the number of replica is under pool's min_size - ceph-users

4 Dec 2020

Hi,

Could you tell me whether read I/O is acxepted when the number of replicas
is under pool's min_size?

I read the official document and found that there is a difference of the
effect of pool's
min_size between pool's document and the pool's configuration document.

Pool's document:
https://docs.ceph.com/en/latest/rados/operations/pools/
...
  To set a minimum number of required replicas for I/O,
you should use the min_size setting.

Pool's configuration document.
https://docs.ceph.com/en/latest/rados/configuration/pool-pg-config-ref/
...
  osd pool default min size Description

Sets the minimum number of written replicas for objects in the pool in
order to acknowledge a write operation to the client.

The former says that min_size is related to both read/write I/O.

On the other hands, the latter says it's only about write I/O. So which is
correct description?

As a result of my verification, the former looks correct.

I created a RGW object in a pool having 3 replicas and its min_size is 2.

Both read and write aren't accepted when 2 replicas are gone.

Thanks,

Satoru