I assume you're talking about "Option Two: MULTI-SITE OBJECT STORAGE
WITH FEDERATED GATEWAYS", from Inktank's
http://info.inktank.com/multisite_options_with_inktank_ceph_enterprise
There are still some options. Each zone has a master and one (or more)
replicas. You can only write to the master zone, but you can read from
the master or replicas. Regions and Zones live inside a Ceph clusters.
Each Ceph cluster can have multiple zones. Each zone has it's own URL
and web servers.
Just like any replication strategy, this can be as simple or complicated
as you want to make it. For example, you could set up a single master
zone in site one that replicates to sites 2 and 3. Or you could setup 3
master zones that replicate in a ring, Site 1 master -> Site 2 replica,
Site 2 master -> Site 3 replica, Site 3 master -> Site 1 replica. It's
more complicated, but it lets everybody read/write to their local
cluster, as long as you're prepared to deal with 6 different URLs.
Which setup you choose really depends on your requirements, and it
changes the answers to the rest of your questions.
*Craig Lewis*
Senior Systems Engineer
Office +1.714.602.1309
Email cle...@centraldesktop.com <mailto:cle...@centraldesktop.com>
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On 4/1/14 10:06 , Shang Wu wrote:
Hi all,
I have some questions about the Ceph multi-site implementation.
I am thinking to have Ceph as the storage solution for across three internal
site. I think, with a good internet connection, using the Multi-site object
storage with RADOS (or RGW) might be a good use here. Thus, each site will have
a MON node and many OSDs and replicate data between each other. With this
implementation, I hope it will allow user to READ/WRITE from/to the local
office and Ceph will take care the replication.
So my question is:
1. How does Ceph know how to retrieve data from the nearest location? (As Ceph
usually calculate where the data is through CRUSH rather than the nearest
location for the user.) Will the data be distributed evenly throughout the
three sites? If not, how can we let user to access the _local copy_ ?
2. Is " Multi-site object storage with RADOS" a good fit for their
implementation? i.e. to READ/Write data To/From their local site? If not,
what is the best way to approach this?
3. Does Ceph use the same ID (object name?) for all its replica? Can we
access(read/write) these replica directly?
4. From this multi-site scenario,
when a user write data to Ceph, will it find the nearest OSD to put the data?
When a user read data, does it always respond from the primary data
set (doesn't matter the location) or respond from the nearest replica copy?
Thanks,
Shang Wu
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