CEPHFS add MDS

[a.davanzo]

Hello
i want to use PVE with ceph for server cephFS.
actually i've an old ceph cluster build as a virtual that i want to replace with PVE for managing CEPH.

in previus cluster i've 3 MDS, 2 active and 1 stanby, i've a lot of connection to this cephfs.

i don't find a way to add more then 1 active MDS to fspool with PVE, i've read by default on pve it's only one.
it's possibile to increase?
how?

Thanks

 

[UdoB]

The official documentation at https://docs.ceph.com/en/latest/architecture/#arch-cephfs seems to suggest that there is one active MDS and additional ones on standby:

The extra ceph-mds instances can be standby, ready to take over the duties of any failed ceph-mds that was active.

And that's what I see here. I have only one CephFS; one MDS is "active" and one is "standby".

In my understanding this is per CephFS. If you have more than one FS there may be multiple active MDS.

Disclaimer: I am not a Ceph expert and may happily proven wrong.

 

[a.davanzo]

The official documentation at https://docs.ceph.com/en/latest/architecture/#arch-cephfs seems to suggest that there is one active MDS and additional ones on standby:



And that's what I see here. I have only one CephFS; one MDS is "active" and one is "standby".

In my understanding this is per CephFS. If you have more than one FS there may be multiple active MDS.

Disclaimer: I am not a Ceph expert and may happily proven wrong.

• Scalability: Multiple ceph-mds instances can be active, and theywill split the directory tree into subtrees (and shards of a singlebusy directory), effectively balancing the load amongst all activeservers.

Combinations of standby and active etc are possible, for examplerunning 3 active ceph-mds instances for scaling, and one standbyinstance for high availability.

 

[alexskysilk]

In my understanding this is per CephFS. If you have more than one FS there may be multiple active MDS.

Thats exactly right. You can add as many MDS's to the cluster, but their function would be dictated by your policies.

To tell the filesystem what you want to do, set your max_mds variable per FS, like so:

ceph fs set [ceph fs name] max_mds [n]

where [ceph fs name] is the fs and [n] is the number. n should normally not be more then 2- but unless your fs and client load are both of sufficient size you'd be better off just leaving it at one active and one standby.

 

[a.davanzo]

Thats exactly right. You can add as many MDS's to the cluster, but their function would be dictated by your policies.

To tell the filesystem what you want to do, set your max_mds variable per FS, like so:

ceph fs set [ceph fs name] max_mds [n]

where [ceph fs name] is the fs and [n] is the number. n should normally not be more then 2- but unless your fs and client load are both of sufficient size you'd be better off just leaving it at one active and one standby.

thanks a lot
i't worked when i've try i've get error i don't know why but now works
thanks a lot