[ceph-users] tuning for backup target cluster

Hi Everyone, I'm putting together a HDD cluster with an ECC pool dedicated to the backup environment. Traffic via s3. Version 18.2, 7 OSD nodes, 12 * 12TB HDD + 1NVME each, 4+2 ECC pool. Wondering if there is some general guidance for startup setup/tuning in regards to s3 object size. Files are read from fast storage (SSD/NVME) and written to s3. Files sizes are 10MB-1TB, so it's not standard s3. traffic. Backup for big files took hours to complete. My first shot would be to increase default bluestore_min_alloc_size_hdd, to reduce the number of stored objects, but I'm not sure if it's a good direccion? Any other parameters worth checking to support such a traffic pattern? Thanks! -- Łukasz