Re: [ceph-users] Help with setting device-class rule on pool without causing data to move

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


Hi David,

CERN has provided with a python script to swap the correct bucket IDs (default <-> hdd), you can find it here :

The principle is the following :
- extract the CRUSH map 
- run the script on it => it creates a new CRUSH file.
- edit the CRUSH map and modify the rule associated with the pool(s) you want to associate with HDD OSDs only like : 
=> step take default WITH step take default class hdd

Then recompile and reinject the new CRUSH map and voilà !

Your cluster should be using only the HDD OSDs without rebalancing (or a very small amount).

In case you have forgotten something, just reapply the former CRUSH map and start again.

Cheers and Happy new year 2019.


On Sun, Dec 30, 2018, 21:16 David C <dcsysengineer@xxxxxxxxx> wrote:
Hi All

I'm trying to set the existing pools in a Luminous cluster to use the hdd device-class but without moving data around. If I just create a new rule using the hdd class and set my pools to use that new rule it will cause a huge amount of data movement even though the pgs are all already on HDDs.

There is a thread on ceph-large [1] which appears to have the solution but I can't get my head around what I need to do. I'm not too clear on which IDs I need to swap. Could someone give me some pointers on this please?

ceph-users mailing list
Ceph-large mailing list

[Index of Archives]     [Information on CEPH]     [Linux Filesystem Development]     [Ceph Development]     [Linux USB Development]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFS]

  Powered by Linux