On 01/09/2014 01:57 PM, MauMau wrote: > From: "Andres Freund" <and...@2ndquadrant.com> >> On 2014-01-08 14:42:37 -0800, Joshua D. Drake wrote: >>> If we have the following: >>> >>> db0->db1:down >>> >>> Using the model (as I understand it) that is being discussed we have >>> increased our failure rate because the moment db1:down we also lose >>> db0. The >>> node db0 may be up but if it isn't going to process transactions it is >>> useless. I can tell you that I have exactly 0 customers that would >>> want that >>> model because a single node failure would cause a double node failure. >> >> That's why you should configure a second standby as another (candidate) >> synchronous replica, also listed in synchronous_standby_names. > > Let me ask a (probably) stupid question. How is the sync rep > different from RAID-1? > > When I first saw sync rep, I expected that it would provide the same > guarantees as RAID-1 in terms of durability (data is always mirrored > on two servers) and availability (if one server goes down, another > server continues full service). What you describe is most like A-sync rep.
Sync rep makes sure that data is always replicated before confirming to writer. Cheers -- Hannu Krosing PostgreSQL Consultant Performance, Scalability and High Availability 2ndQuadrant Nordic OÜ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers