>
> So the Intel 710 kind of sucks latency wise. Is it because it is also
> heavily reading, and maybe WAL should not be put on it?
A couple quick thoughts:
1. There are a lot of moving parts in the system besides the SSDs.
It will take some detailed analysis to determine the cause for the
outlying high latency transactions. The cause may not be as simple
as one SSD processes I/O operations less quickly than another.
For example the system may be subject to some sort of
starvation issue in PG or the OS that is affected by quite
small differences in underlying storage performance.
2. What are your expectations for maximum transaction latency ?
In my experience it is not possible to guarantee sub-second
(or even sub-multi-second) latencies overall in a system
built with general purpose OS and database software.
(put another way : a few outlying 1 second and even
several-second transactions would be pretty much what
I'd expect to see on a database under sustained saturation
load as experienced under a pgbench test).