Hi All, We are running a 5 year old 15 node Ceph cluster with spinners for data and NVMe for DB/Wal. After the recent upgrade to Squid (from Reef) some users reported issues with fluctuating (often bad) disk performance especially affecting k8s etcd. They point to the change to bluestore_prefer_deferred_size_hdd claiming that it's detrimental to the "synchronous write patter" of escd. They also point to submitted_deferred_writes and issued_deferred_writes claiming that there is a massive and growing backlog of deferred writes. I'm not 100% correct that this is the issue but I'm having a hard time finding any relevant information (bad google-fu?) especially about what submitted and issued deferred writes actually represents and why the difference between issued - submitted keeps growing. Anyone got some insights to share? Thanks in advance Magnus