Hi all, my team struggles with enabling rbd caching with Jewel clusters. In Hammer, we successfully use rbd caching with the `writethrough until flush` directive set to true and we get expected IOPS numbers. However, with the same configuration using Jewel, IOPS drops; after analyzing logs it seems to us that the writeback caching mechanism never gets enabled regardless of flush request is being sent. We found a bug entry describing an issue similar to ours: http://tracker.ceph.com/issues/16654 As our note #3 says, we concluded that it seems that the imagecontext user_flushed() signal is missing from the later version, therefore the caching mechanism will never be switched to writeback. Our questions are these: 1) is this change intentional and one needs to configure their environment differently? If yes, how? 2) documentation states that this workaround is only needed with older virtio kernel driver too old. With newer kernels, what would be the possible implications of setting `rbd cache writethrough until flush` to false? Is my understanding correct that this virtio driver version what matters is that is *in the VM*? Thanks, Mark -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
