第 4 章 为 Ceph 存储扩展集群

In a stretch cluster, when a site goes down and the cluster enters a degraded state, the min_size of the pool may be temporarily reduced (e.g., to 1) to allow the placement groups (PGs) to become active and continue serving I/O. However, the size of the pool remains unchanged. The peering_crush_bucket_count stretch mode flag ensures that PGs does not become active unless they are backed by OSDs in a minimum number of distinct CRUSH buckets (e.g., different data centers). This mechanism prevents the system from creating redundant copies solely within the surviving site, ensuring that data is only fully replicated once the downed site recovers.

In a stretch cluster, when a site goes down and the cluster enters a degraded state, the min_size of the pool may be temporarily reduced (e.g., to 1) to allow the placement groups (PGs) to become active and continue serving I/O. However, the size of the pool remains unchanged. The peering_crush_bucket_count stretch mode flag ensures that PGs does not become active unless they are backed by OSDs in a minimum number of distinct CRUSH buckets (e.g., different data centers). This mechanism prevents the system from creating redundant copies solely within the surviving site, ensuring that data is only fully replicated once the downed site recovers.