I am curious what the kernel parts of ceph do? What the user parts do? Do we have a web page describing this in detail? >From what you described, in the librbd case, user parts do not need the kernel parts at all, right? This sounds very good to me. Send from my iOS device. On Jan 20, 2013, at 2:16 AM, Sage Weil <sage@xxxxxxxxxxx> wrote: > On Sat, 19 Jan 2013, Jeff Mitchell wrote: >> Sage Weil wrote: >>> On Sun, 20 Jan 2013, Peter Smith wrote: >>>> Thanks for the reply, Sage and everyone. >>>> >>>> Sage, so I can expect Ceph-rbd works well on Centos 6.3 if I only use >>>> it as the Cinder volume backend because the librbd in QEMU doesn't >>>> make use of kernel client, right? >>> >>> Then the dependency is on the qemu version. I don't remember that off the >>> top of my head, or know what version rhel6 ships. Most people deploying >>> openstack and rbd are using a more modern distro (like ubuntu 12.04). >> >> This discussion has made me curious: I'm using Ganeti to manage VMs, which >> manages the storage using the kernel client and passes in the dev device to >> qemu. >> >> Can you comment on any known performance differences between the two methods >> -- native qemu+librbd creating a block device vs. the kernel client creating a >> block device? > > librbd is faster-paced and has more features, including client-side > caching (analogous to the cache in a hard drive), discard, and support for > image cloning. It tends to perform better. > > The kernel client can be combined with FlashCache or something similar, > although that isn't something we've tested. > > We generally recommend the KVM+librbd route, as it is easier to manage the > dependencies, and is well integrated with libvirt. FWIW this is what > OpenStack and CloudStack normally use. > > sage -- 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
