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.
Eric
On Sun, Dec 30, 2018, 21:16 David C <dcsysengineer@xxxxxxxxx> wrote:
_______________________________________________Hi AllI'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?
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