Ceph Primary Affinity

约定不等于承诺〃 2023-10-09 13:12 22阅读 0赞

## Ceph Primary Affinity ##

This option allows you to answer a fairly constant worry in the case of heterogeneous cluster. Indeed, all HDD do not have the same performance or not the same ratio performance / size.  
With this option, it is possible to reduce the load on a specific disk without reducing the amount of data it contains.  
Furthermore, the option is easy to modify because it does not result in data migration. Only preference between primary / secondary will be modified and propagated to clients.

Before playing with cluster options and tune crushmap, remember to verify that your client is compatible with those options.

> You must enable ‘mon osd allow primary affinity = true’ on the mons before you can adjust primary-affinity. note that older clients will no longer be able to communicate with the cluster.

( For client kernel module you can have a look to [http://cephnotes.ksperis.com/blog/2014/01/21/feature-set-mismatch-error-on-ceph-kernel-client.][http_cephnotes.ksperis.com_blog_2014_01_21_feature-set-mismatch-error-on-ceph-kernel-client.] )

Look if the monitor has the primary affinity option:  
\# ceph –admin-daemon /var/run/ceph/ceph-mon.\*.asok config show | grep ‘primary\_affinity’  
“mon\_osd\_allow\_primary\_affinity”: “false”,

Edit ceph.conf dans add in section \[mon\]:  
mon osd allow primary affinity = true

Reload mon and test.  
We look how many pg is primary on osd.0, and how many is secondary :

Try to change primary affinity :

Now there will be no more reading on this OSD.

[http_cephnotes.ksperis.com_blog_2014_01_21_feature-set-mismatch-error-on-ceph-kernel-client.]: http://cephnotes.ksperis.com/blog/2014/01/21/feature-set-mismatch-error-on-ceph-kernel-client.