[ceph-users] Cluster network slower than public network

David Turner drakonstein at gmail.com
Thu Nov 16 07:20:51 PST 2017


There is another thread in the ML right now covering this exact topic.  The
general consensus is that for most deployments, a separate network for
public and cluster is wasted complexity.

On Thu, Nov 16, 2017 at 9:59 AM Jake Young <jak3kaj at gmail.com> wrote:

> On Wed, Nov 15, 2017 at 1:07 PM Ronny Aasen <ronny+ceph-users at aasen.cx>
> wrote:
>
>> On 15.11.2017 13:50, Gandalf Corvotempesta wrote:
>>
>> As 10gb switches are expansive, what would happen by using a gigabit
>> cluster network and a 10gb public network?
>>
>> Replication and rebalance should be slow, but what about public I/O ?
>> When a client wants to write to a file, it does over the public network
>> and the ceph automatically replicate it over the cluster network or the
>> whole IO is made over the public?
>>
>>
>>
>> public io would be slow.
>> each write goes from client to primary osd on public network, then is
>> replicated 2 times to the secondary osd's over the cluster network, then
>> the client is informed the block is written.
>> since cluster network would see 2x write traffic compared to public
>> network when things a OK. and many times the traffic of the public network
>> when things are recovering or backfilling. i would prioritize the
>> clusternetwork for the highest speed if one could not have 10Gbps on
>> everything.
>>
>
>
> I would seriously consider combining the cluster and public network. It
> will simplify your configuration.   It really takes a lot to saturate a 10G
> network with Ceph.
>
> If you find that you need to separate your public and cluster networks
> later, you can do that in the future.
>
> Jake
>
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