Den mån 23 sep. 2024 kl 16:23 skrev Stefan Kooman <stefan@bit.nl>:
On 23-09-2024 16:04, Dave Hall wrote:
Thank you to everybody who has responded to my questions.
At this point I think I am starting to understand. However, I am still trying to understand the potential for data loss.
In particular:
- In some ways it seems that as long as there is sufficient OSD capacity available the worst that can happen from a bad crush map is poor placement and poor performance. Is this correct?
If you would have a (new) crush rule without any OSD mappings all PGs for pools that use that rule would go in an inactive state, i.e. downtime. So when you create a (new) rule you would have to check that CRUSH can indeed find enough OSDs to comply with the policy you defined.
Are you sure? I have asked some pools to use an "impossible" crush rule after creation and the PGs only end up as "misplaced". At creation they might stay inactive until a good place for them can be found, but then you can't write data to it so it is not a "data-loss" scenario really if the pool never started.