MinIO site replication has no cross-site quorum, and its replication queue exists only inside the source cluster: lose that site and the un-replicated backlog is gone and un-enumerable. Sync mode costs latency without fixing that. The precise model, the RTO/RPO table, and the DR patterns that match real SLAs.
MinIO has no NameNode. It puts the namespace on XFS as real directories and xl.meta files. On Lots of Small Files that means you can exhaust inodes while df -h still looks fine, and a flat leaf can stall PUT, LIST, scanner, and ILM together. Here is the on-disk model, the inode math, and a prefix recipe that keeps XFS inside a regime you can operate.
MinIO fixed the HDFS NameNode limit, but it has no index: it writes one xl.meta per object on every drive of the erasure set. On 5 servers of 12 NVMe, MinIO picks a 15-wide set by default, so each small object is stored 15 times over. A worked sizing that looks fine for two years and dies in days.
MinIO was not built for Lots of Small Files (LOSF). No global index, no read repair, and a scanner that can take weeks to notice silent corruption. Here is what breaks, why tiering makes it worse, and when you should use a database instead.