Planet Ceph

Aggregated news from external sources

October 1, 2011

v0.36 released

It’s been three weeks and v0.36 is ready.  The most visible change this time around is that the daemons and tools have been renamed.  Everything that used to start with ‘c’ now starts with ‘ceph-’, and libceph is now libcephfs.  Nothing earth shattering, but we’re trying to clean these things up where we can and deal with the pain sooner rather than later.  (If you have any naming or tool usage pet peeves, let us know.)

Notable changes since v0.35:

  • librbd: api supports progress callbacks
  • librbd: python bindings (enabling our Openstack integration)
  • librbd: async writes (big write performance improvement)
  • libceph/cfuse: many fixes
  • osd: many fixes

The biggest item here is probably the librbd async write change, which affects qemu/KVM virtual machines using the RBD virtual disks.  Typical physical disk have a write cache and don’t actually ensure your data is physically written to the platter until you issue a flush command (which modern file systems are now careful to do at critical points).  In contrast, RBD wouldn’t acknowledge a write until it was written to the backend storage (all N replicas), which meant high latency writes and seemingly poor performance (even though throughput was theoretically very good).  librbd now buffers writes so that it behaves more like a disk, resulting in vastly improved performance for most typical workloads (like dd).  You still need to use the latest upstream qemu version to ensure that flush commands are properly handled, so this is still off by default; see this post for more information.  We haven’t made the same change to the Linux kernel RBD driver, but it’s coming soon.

We took an extra week this cycle due to a few trips (Yehuda, Bryan, and I were in Israel for a few days, and then I was at SDC last week), and may do that again this sprint.  Tommi and Bryan will be at the Openstack conference and design summit (don’t miss Tommi’s talk on RBD on Friday!) next week, and you’ll see us in the Dell booth provisioning a Ceph cluster with Chef and Dell’s crowbar.

For v0.37, the focus is on Chef cookbooks, Openstack integration, radosgw scalability improvements, and libvirt integration.

You can get v0.36 from: