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no data points returned from metric query

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Dear Admin

I found that the ram utilization reaches at about 75 - 95 % in ALL   nodes.  ( 3 management + 4 storage)

The iscsi function is fine. The cluster is still normal.

But the management nodes are not stable. It will be down for 10 - 20 seconds.

Now, there is a problem : no data points returned from metric query

https://ibb.co/hsf3qU

How to solve it?

Thanks!

Ben

How much ram do you have per node ? how may osds per node ? do you use hdd or ssd ?

Node  1-3 are running in VM server with 2GB ram only

Node 4 and Node 7 with 40 GB Ram, having 6 OSD, all are SSD, no journal disk, each disk is 1TB

Node 5 and Node 6 with 32GB Ram, having 6 OSD, all are SSD, no journal disk,  each disk is 1TB

The cluster is connecting to 2 VM server with 5 TB respectively.

No of PG is 1024, replicas is 2.

https://ibb.co/kDPSjp

https://ibb.co/m8eXH9

https://ibb.co/hhmq4p

Now, the cluster storage and VM servers are still running normally.

Thanks, for your help and answer.

Ben

Most likely the stats function failed due to memory, but as you stated the entire cluster will not be stable as well. You should try to avoid high ram % usage. You may want to increase your ram on your management nodes to 4M

You should also considering lowering your osd cache memory via

bluestore_cache_size_ssd = 1GB

(the default value is 3G for bluestore) in your /etc/ceph/xx.conf file and restart osd services  manually or reboot.

if this still does not solve it let me know

 

Admin

 

Noted, I try now, thanks for your solution given

 

Ben

 

Admin

 

I just added the RAM to 4G on ALL management nodes.

Afterwards, I reboot all servers, the problem of "no data points returned from metric query' has been solved.

Thanks for your help.

By the way, I will try to add more RAM on the OSD data storage server. It seems that 32 GB is not enough.

https://ibb.co/kQ4hH9

Ben

Hi Admin

The storage and iscsi server has 32GB ram. There is 1 OS disk and 7 OSD SSD disks.

According to your hardware recommendation document, 2GB per disk and 16GB for iscsi service. So, my sever meets the hardware requirement.

8 * 2GB + 16GB + 32GB

But now, the RAM utilization is almost 100%. Is it normal? Shall I add more RAM?

https://ibb.co/fGOUx9

https://ibb.co/ju9oPp

Ben

 

 

 

Re using EVO disks, please see my post on SSD performance

Thanks, I will try to replace the enterprises SSD or HDD

Re adding RAM, yes it is better. else set

bluestore_cache_size_ssd = 1GB

as indicated earlier.

You are correct, there are recent bluestore OSD tunings for SSDs that do use more memory than what the Ceph and PetaSAN docs state.

https://www.spinics.net/lists/ceph-devel/msg40592.html

We will change it

 

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