Thanks for your answer MON-MGR hosts have a mgmt network and a public network. OSD nodes have instead a mgmt network, a public network. and a cluster network This is what I have in ceph.conf: public network = 192.168.61.0/24 cluster network = 192.168.222.0/24 public and cluster networks are 10 Gbps networks (actually there is a single 10 Gbps NIC on each node used for both the public and the cluster networks). The mgmt network is a 1 Gbps network, but this one shouldn't be used for such pings among the OSDs ... Cheers, Massimo On Thu, Jan 30, 2020 at 9:26 AM Stefan Kooman <stefan@bit.nl> wrote:
Quoting Massimo Sgaravatto (massimo.sgaravatto@gmail.com):
After having upgraded my ceph cluster from Luminous to Nautilus 14.2.6 , from time to time "ceph health detail" claims about some"Long heartbeat ping times on front/back interface seen".
As far as I can understand (after having read https://docs.ceph.com/docs/nautilus/rados/operations/monitoring/), this means that the ping from one OSD to another one exceeded 1 s.
I have some questions on these network performance checks
1) What is meant exactly with front and back interface ?
Do you have a "public" and a "cluster" network? I would expect that the "back" interface is a "cluster" network interface.
2) I can see the involved OSDs only in the output of "ceph health detail" (when there is the problem) but I can't find this information in the log files. In the mon log file I can only see messages such as:
2020-01-28 11:14:07.641 7f618e644700 0 log_channel(cluster) log [WRN] : Health check failed: Long heartbeat ping times on back interface seen, longest is 1416.618 msec (OSD_SLOW_PING_TIME_BACK)
but the involved OSDs are not reported in this log. Do I just need to increase the verbosity of the mon log ?
3) Is 1 s a reasonable value for this threshold ? How could this value be changed ? What is the relevant configuration variable ?
Not sure how much priority Ceph gives to this ping check. But if you're on a 10 Gb/s network I would start complaining when things take longer than 1 ms ... a ping should not take much longer than 0.05 ms so if it would take an order of magnitude longer than expected latency is not optimal.
For Gigabit networks I would bump above values by an order of magnitude.
Gr. Stefan
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