There's no significant change with the global EC clusters story in the 2.7 release. That's something we're discussing next week at the summit.
--John On 19 Apr 2016, at 22:47, Mark Kirkwood wrote: > Hi, > > Has the release of 2.7 significantly changed the assessment here? > > Thanks > > Mark > > On 15/02/16 23:29, Kota TSUYUZAKI wrote: >> Hello Mark, >> >> AFAIK, a few reasons for that we still are in working progress for erasure >> code + geo replication. >> >>>> and expect to survive a region outage... >>>> >>>> With that I mind I did some experiments (Liberty swift) and it looks to me >>>> like if you have: >>>> >>>> - num_data_frags < num_nodes in (smallest) region >>>> >>>> and: >>>> >>>> - num_parity_frags = num_data_frags >>>> >>>> >>>> then having a region fail does not result in service outage. >> >> Good point but note that the PyECLib v1.0.7 (pinned to Kilo/Liberty stable) >> still have a problem which cannot decode the original data when all feed >> fragments are parity frags[1]. (i.e. if set >> num_parity_frags = num_data frags and then, num_parity_frags comes into >> proxy for GET request, it will fail at the decoding) The problem was already >> resolved in the PyECLib/liberasurecode at master >> branch and current swift master has the PyECLib>=1.0.7 dependencies so if >> you thought to use the newest Swift, it might be not >> a matter. >> >> In the Swift perspective, I think that we need more tests/discussion for geo >> replication around write/read affinity[2] which is geo replication stuff in >> Swift itself and performances. >> >> For the write/read affinity, actually we didn't consider the affinity >> control to simplify the implementation until EC landed into Swift master[3] >> so I think it's time to make sure how we can use the >> affinity control with EC but it's not done yet. >> >> For the performance perspective, in my experiments, more parities causes >> quite performance degradation[4]. To prevent the degradation, I am working >> for the spec which makes duplicated copy from >> data/parity fragments and spread them out into geo regions. >> >> To sumurize, we've not done the work yet but we welcome to discuss and >> contribute for EC + geo replication anytime, IMO. >> >> Thanks, >> Kota >> >> 1: >> https://bitbucket.org/tsg-/liberasurecode/commits/a01b1818c874a65d1d1fb8f11ea441e9d3e18771 >> 2: >> http://docs.openstack.org/developer/swift/admin_guide.html#geographically-distributed-clusters >> 3: >> http://docs.openstack.org/developer/swift/overview_erasure_code.html#region-support >> 4: >> https://specs.openstack.org/openstack/swift-specs/specs/in_progress/global_ec_cluster.html >> >> >> >> (2016/02/15 18:00), Mark Kirkwood wrote: >>> After looking at: >>> >>> https://www.youtube.com/watch?v=9YHvYkcse-k >>> >>> I have a question (that follows on from Bruno's) about using erasure coding >>> with geo replication. >>> >>> Now the example given to show why you could/should not use erasure coding >>> with geo replication is somewhat flawed as it is immediately clear that you >>> cannot set: >>> >>> - num_data_frags > num_devices (or nodes) in a region >>> >>> and expect to survive a region outage... >>> >>> With that I mind I did some experiments (Liberty swift) and it looks to me >>> like if you have: >>> >>> - num_data_frags < num_nodes in (smallest) region >>> >>> and: >>> >>> - num_parity_frags = num_data_frags >>> >>> >>> then having a region fail does not result in service outage. >>> >>> So my real question is - it looks like it *is* possible to use erasure >>> coding in geo replicated situations - however I may well be missing >>> something significant, so I'd love some clarification here [1]! >>> >>> Cheers >>> >>> Mark >>> >>> [1] Reduction is disk usage and net traffic looks attractive >>> >>> __________________________________________________________________________ >>> OpenStack Development Mailing List (not for usage questions) >>> Unsubscribe: [email protected]?subject:unsubscribe >>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >>> >>> >> >> > > > __________________________________________________________________________ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: [email protected]?subject:unsubscribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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