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This could be explained by your osds not being able to communicate with each other. We have 2 vlans between our storage nodes, the public and private networks for ceph to use.
We added 2 new nodes in a new rack on new switches and as soon as we added a single osd for one of them to the cluster, the peering never finished and we had a lot of blocked requests that never went away.
In testing we found that the rest of the cluster could not communicate with these nodes on the private vlan and after fixing the network switch config, everything worked perfectly for adding in the 2 new nodes. If you are using a basic network configuration with only one network and/or vlan, then this is likely not to be your issue. But to check and make sure, you should test pinging between your nodes on all of the IPs they have.
From: ceph-users [ceph-users-bounces@xxxxxxxxxxxxxx] on behalf of Helander, Thomas [Thomas.Helander@xxxxxxxxxxxxxx]
Sent: Monday, August 01, 2016 10:06 AM To: ceph-users@xxxxxxxxxxxxxx Subject: [ceph-users] Read Stalls with Multiple OSD Servers Hi,
I’m running a three server cluster (one monitor, two OSD) and am having a problem where after adding the second OSD server, my read rate drops significantly and eventually the reads stall (writes are improved as expected). Attached is a log of the rados benchmarks for the two configurations and below is my hardware configuration. I’m not using replicas (capacity is more important than uptime for our use case) and am using a single 10GbE network. The pool (rbd) is configured with 128 placement groups.
I’ve checked the CPU utilization of the ceph-osd processes and they all hover around 10% until the stall. After the stall, the CPU usage is 0% and the disks all show zero operations via iostat. Iperf reports 9.9Gb/s between the monitor and OSD servers.
I’m looking for any advice/help on how to identify the source of this issue as my attempts so far have proven fruitless…
Monitor server: 2x E5-2680V3 32GB DDR4 2x 4TB HDD in RAID1 on an Avago/LSI 3108 with Cachevault, configured as write-back 10GbE
OSD servers: 2x E5-2680V3 128GB DDR4 2x 8+2 RAID6 using 8TB SAS12 drives on an Avago/LSI 9380 controller with Cachevault, configured as write-back. - Each RAID6 is an OSD 10GbE
Thanks,
Tom Helander
KLA-Tencor
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