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).
The cost is reasonable with RAID-1. The sync rep requires high cost to get
both durability and availability --- three servers.
Am I expecting too much?
Regards
MauMau
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