First I need to say that I'm asking this question on behalf of "a
friend", who asked me what I thought on the subject -- I host all the
databases important to me and my livelihood, on physical machines I own
outright. That said, I'm curious as to the current thinking on a)
whether it is wise, and b) if so how to deploy, PG servers on AWS. As I
recall, a couple years ago it just wasn't a wise plan because Amazon's
I/O performance and reliability wasn't acceptable. Perhaps that's no
longer the case..
Just to set the scene -- the application is a very high traffic web
service where any down time is very costly, processing a few hundred
transactions/s.
Scanning through the latest list of AWS instance types, I can see two
plausible approaches:
1. High I/O Instances: (regular AWS instance but with SSD local
storage) + some form of replication. Replication would be needed because
(as I understand it) any AWS instance can be "vanished" at any time due
to Amazon screwing something up, maintenance on the host, etc (I believe
the term of art is "ephemeral").
2. EBS-Optimized Instances: these allow the use of EBS storage (SAN-type
service) from regular AWS instances. Assuming that EBS is maintained to
a high level of availability and performance (it doesn't, afaik, feature
the vanishing property of AWS machines), this should in theory work out
much the same as a traditional cluster of physical machines using a
shared SAN, with the appropriate voodoo to fail over between nodes.
Any thoughts, wisdom, and especially from-the-trenches experience, would
be appreciated.
In the Googlesphere I found this interesting presentation :
http://www.pgcon.org/2012/schedule/attachments/256_pg-aws.pdf which
appears to support option #2 with s/w (obviously) RAID on the PG hosts,
but with replication rather than SAN cluster-style failover, or perhaps
in addition to.
Note that I'm not looking for recommendations on PG hosting providers
(in fact my friend is looking to transition off one of them, to bare-AWS
machines, for a variety of reasons).
Thanks.
