[Openstack] Swift new starter questions (PoC)

Chris contact at progbau.de
Mon Aug 8 14:56:41 UTC 2016


We are currently playing with swift and try to find out if it would be 
useful for our needs. We would use the latest mitaka release. It would 
be a multi-region deployment in around 4-5 different countries/DCs with 
a total size of 5 TB and millions of small files. Worst case RTT between 
two locations would be 400ms. I came across some questions I want to ask.

1) As far as I understood Swift returns a 200 OK if the majority of 
replicas are written. Is it possible to change this ratio?
2) Does the write affinity now includes containers and accounts? Saw a 
presentation from the Symantic guys on the Openstack summit where this 
topic came up. And the acces time spikes if this information are 
transferred from the WAN.
2a) If not does it make sense to do some kind of warm up and get the 
container and account information saved in memcache for faster access? 
Anybody experience at this approach?
3) Lets say we have 5 regions and a replication factor of 3. When we use 
write affinity 12 copies would be written in a local cluster and then in 
the background replicated to the other regions? Isn't there a better way 
and avoid unnecessary local writes if they would be transferred away anyway?
4) What will happen if the WAN connection to a DC fails is there an 
option to not create a another replication in other DCs just because the 
WAN is of fore some minutes?
5) In a Swift multi region deployment is it possible to have local 
Keystone services in every region/DC or does all authentication need to 
come from the same keytone machine?

Any help and ideas appreciated!


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