[ceph-users] Cluster network slower than public network

Ronny Aasen ronny+ceph-users at aasen.cx
Wed Nov 15 10:07:09 PST 2017


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.

kind regards
Ronny Aasen
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