On 7/28/22 22:41, Mark Selby wrote:
We use Ceph RBD/FS extensively and are starting down our RGW journey. We
have 3 sites and want to replicate buckets from a single "primary" to
multiple "backup" sites. Each site has a Ceph cluster and they are all
configured as part of a Multisite setup.
I am using the examples at
https://docs.ceph.com/en/quincy/radosgw/multisite-sync-policy and have
gotten a directional sync to work using the below commands.
The question I have is about the scalability of what I am doing. How
groups/flows/pipe all fit together is not very clear in the docs.
My group 'us' has two flows, 'dev1-to-dev2' and 'dev1-to-dev3'.
The pipe that I create specifies the group 'us' but does not specify the
flows to us. I have to assume in this case it uses all of the flows at
the zonegroup level. This is fine as long as these are the only flows
that I will ever need.
yes, in your setup, it uses the flows created for the group "us"
(zone-group level).
What I am try having difficulty understanding is the linkage between
pipes and flows. If any one can explain this more than the docs do, it
would be greatly appreciated.
A data-flow defines the flow of data between the different zones (either
symmetrical or directional) where as a pipe defines actual buckets that
can use these data flows [1]
FWIU, pipes use the data-flows associated with their group policy or
inherits the ones configured at zone-group level.
i.e.,
* if the group policy is created at zonegroup level (like in your setup
'us'), pipes of that group use the flows associated with that <group-id>
('us'). If no flows are configured, the sync is not allowed.
* In case if the group (say, 'us-bucket') is created at bucket-level,
the data-flows (if any) created for that group ('us-bucket') should be
subset of what zonegroup level policy ('us') allows. And that group
policy ('us-bucket') pipes use the flows in the following order
(a) the data-flows created for that bucket-level group policy ('us-bucket')
(b) if no flows are created, it then inherits the data flow allowed at
zonegroup level ('us').
Hope this helps!
-Soumya
[1] https://docs.ceph.com/en/quincy/radosgw/multisite-sync-policy/
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