[ceph-users] Cluster network slower than public network

Jake Young jak3kaj at gmail.com
Thu Nov 16 06:59:07 PST 2017


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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