Hi Chuck, Many thanks for your comments! I have replied on the blog.
Best regards, Vincenzo. 2014-06-12 21:10 GMT+02:00 Chuck Thier <cth...@gmail.com>: > Hi Vincenzo, > > First thank you for this work. It is always interesting to see > different data points from different use cases. > > I noticed a couple of things and would like to ask a couple of questions > and make some observations. > > Comparing a high level HTTP/REST based api (swift) to a low-level C > based api (librados) is not quite an apples to apples comparison. A more > interesting comparison, or at least another data point would be to run the > same tests with the rados gateway which provides a REST based interface. I > believe that what you attribute to differences between the performance of > the CRUSH algorithm and swift's ring are more likely attributed to the > extra overhead of a high level interface. > > An optimization is made for ceph by adding an extra disk to store the > journal, which specifically enhances the the small object performance, for > a total of 3 spindles per node. Yet, swift was only given 2 spindles per > node, thus giving ceph quite a substantial more overall IO to work with. > > In several of the results, the graphs show a significant reduction of > throughput with swift going from 1 container to 20 containers with the same > sized object. In a correctly configured swift cluster, performance for > PUTs at high concurrency will always be faster with more containers. > Container operations are not part of the GET path, so the number of > containers will not effect GET performance. This leads me to believe that > either swift isn't properly configured, or the client is doing something > non-optimal for those cases. > > The eventual consistency semantics of swift are reported incorrectly. > For 3 replicas, swift will stream out all 3 copies of the object to their > locations at the same time, and only return success if at least 2 of those > are successful. This is somewhat similar to the behavior of ceph. > Replication in swift is only used when there are failures. > > I would also suggest expanding the data set a bit. For example, test > the performance after the system has been filled more than 50%. I would > also highly recommend testing performance when there are failures, such as > a dead disk, or one of the nodes going away. > > Thanks, > > -- > Chuck > > > On Thu, Jun 12, 2014 at 3:46 AM, Vincenzo Pii <p...@zhaw.ch> wrote: > >> As promised, the results for our study on Ceph vs Swift for object >> storage: >> http://blog.zhaw.ch/icclab/evaluating-the-performance-of-ceph-and-swift-for-object-storage-on-small-clusters/ >> >> >> 2014-06-06 20:19 GMT+02:00 Matthew Farrellee <m...@redhat.com>: >> >>> On 06/02/2014 02:52 PM, Chuck Thier wrote: >>> >>> I have heard that there has been some work to integrate Hadoop with >>>> Swift, but know very little about it. Integration with MS exchange, but >>>> could be an interesting use case. >>>> >>> >>> nutshell: the hadoop ecosystem tends to integrate with mapreduce or >>> hdfs. hdfs is the hadoop implementation of a distributed file system >>> interface. there are a handful of others - >>> http://wiki.apache.org/hadoop/HCFS - including one for swift. so where >>> you might access a file in via hdfs:///... you can also swift:///... for >>> processing by mapreduce or other frameworks in hadoop. >>> >>> best, >>> >>> >>> matt >>> >>> >>> >>> _______________________________________________ >>> Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/ >>> openstack >>> Post to : openstack@lists.openstack.org >>> Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/ >>> openstack >>> >> >> >> >> -- >> Vincenzo Pii >> Researcher, InIT Cloud Computing Lab >> Zurich University of Applied Sciences (ZHAW) >> http://www.cloudcomp.ch/ >> >> _______________________________________________ >> Mailing list: >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack >> Post to : openstack@lists.openstack.org >> Unsubscribe : >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack >> >> > -- Vincenzo Pii Researcher, InIT Cloud Computing Lab Zurich University of Applied Sciences (ZHAW) http://www.cloudcomp.ch/
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