On 04/15/2018 08:18 PM, Robert Stanford wrote:
Iperf gives about 7Gb/s between a radosgw host and one of my OSD hosts (8 disks, 8 OSD daemons, one of 3 OSD hosts). When I benchmark radosgw with cosbench I see high TCP retransmission rates (from sar -n ETCP 1). I don't see this with iperf. Why would Ceph, but not iperf, cause high TCP retransmission rates?
Most probably your application (radosgw in this case) is not able to process requests fast enough and some packets are dropped.
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