> > What I don't see streaming working for is DR drills. I need to, in a > controlled manner, move the entire application to the secondary datacenter, > while keeping all the nodes in sync, make sure everything operates properly > from there (which means allowing database updates), then move it all back > to the primary datacenter, without losing sync on any slaves (this is a 2T > database, which I'm sure isn't the largest anyone has dealt with, but it > means that reseeding slaves is a multi-hour endeavour). With Slony, these > drills are easy: a single slonik command relocates the master to the DR > datacenter while keeping everything in sync, and when testing is complete, > another slonik command puts everything back the way it was, without any > data loss and with minimal chance for human error.
I guess I got your point :) Agree to you now! :) With v9.3 I think I would be easy to swap the roles for primary and DR. (I need to test this before I can say for sure). But still it will be a pain if one needs to shift all the operations to DR (which is a a valid case, e.g. you would do that for testing the readiness of your DR site by doing a mock failover) and then shift back to Primary Site (assuming while operations were going on on DR site, primary site was kept down purposefully). This will involve taking a backup from DR to primary and then swapping the roles. I guess this limitation will be soon waived off. I guess v9.4 or next one should have this feature (no backups as long as your wal_keep_segment is high enough to cater to your testing/mock failover window). I agree slonik and few other utilities/tool around it administration/management is quite easy. If you feel that the current implementation of streaming replication is > able to do that task, then I'll have to move up my timetable to re-evaluate > it. It _has_ been a few versions since I've taken a good look at it. Given your expectation above, v9.3 is a good candidate. But you can afford to give it a miss. You must try once v9.4 is out. Regards Sameer Ashnik Pte. Ltd. Singapore
