[openstack-dev] [Swift] Erasure coding and geo replication
mark.kirkwood at catalyst.net.nz
Mon Feb 15 09:00:49 UTC 2016
After looking at:
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
- 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 !
 Reduction is disk usage and net traffic looks attractive
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