On http://pve.proxmox.com/wiki/Storage:_Ceph there's a .conf file example: . . . [mon] [mds] [osd] osd journal = /srv/journal/osd.$id.journal ;only if you want put journal on a dedicated disk, like ssd osd journal size = 1000 ; uncomment the following line if you are mounting with ext4 ; filestore xattr use omap = true ; uncomment if you want journal on tmpfs ;journal dio = false "journal dio" is only set for tmpfs devices and not real devices? Seems like setting that to yes for all devices would help performance.