Mastering Proxmox - Third Edition

OSD journal

In Ceph, any I/O writes are first written to a journal before they are transferred to the actual OSD. Journals are simply smaller partitions that accept smaller bits of data at a time while the backend OSDs catch up with the writes. By putting journals on faster-access disk drives, such as SSDs, we can increase a Ceph operation significantly, since user data is written to a journal at a higher speed while the journal sends short bursts of data to OSDs, giving them time to catch up. Journals for multiple OSDs can be stored in one SSD per node. Alternatively, OSDs can be divided into multiple SSDs. For a small cluster of up to eight OSDs per node, using an SSD improves performance. However, while working with a larger cluster with ...