[jira] [Commented] (HDDS-9280) Quasi-closed container with unhealthy replicas may remain under-replicated in 4 node cluster

["Siddhant Sangwan (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDDS-9280?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17765064#comment-17765064 ] 

Siddhant Sangwan commented on HDDS-9280:
----------------------------------------

I have some initial thoughts on this, where we can delete a replica to make space depending on its sequence id:
 !Quasi_dilemma.png! 

> Quasi-closed container with unhealthy replicas may remain under-replicated in 4 node cluster
> --------------------------------------------------------------------------------------------
>
>                 Key: HDDS-9280
>                 URL: https://issues.apache.org/jira/browse/HDDS-9280
>             Project: Apache Ozone
>          Issue Type: Bug
>          Components: SCM
>            Reporter: Ethan Rose
>            Priority: Major
>         Attachments: Quasi_dilemma.png
>
>
> This is a follow-up based on discussion around HDDS-8536 in this [PR|https://github.com/apache/ozone/pull/5255#discussion_r1322165405]. Replication manager will try to keep all replicas with unique origin node IDs for quasi-closed containers that cannot be closed, while fully replicating the healthy replicas. This could require up to 5 replicas to satisfy, for example:
> SCM state: Quasi-closed
> Replica states: quasi-closed(origin 1) quasi-closed(origin 1) quasi-closed(origin 1) unhealthy(origin 2) unhealthy(origin 3)
> In a 4 node cluster, or a 5 node cluster trying to decommission a node, this would remain under-replicated or get stuck. In this case, we need to choose how to proceed.



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