On Tue, Nov 26, 2013 at 11:31 AM, Josh Berkus <josh@agliodbs.com> wrote:
> On 11/25/2013 12:01 PM, Lee Nguyen wrote:
>> Hi,
>>
>> Having attended a few PGCons, I've always heard the remark from a few
>> presenters and attendees that Postgres shouldn't be run inside a VM. That
>> bare metal is the only way to go.
>
> This is pretty dated advice. Early VMs had horrible performance under
> load, which is mostly where this thinking comes from. It's not true
> anymore.
>
> It *is* true that getting good performance in a virtualized environment
> requires more tuning than bare metal, because you have to tune the VM
> system as well.
>
>> Here at work we were entertaining the idea of running our Postgres database
>> on our VM farm alongside our application vm's. We are planning to run a
>> few Postgres synchronous replication nodes.
>
> Biggest pitfall here is IO performance configuration. I can't give you
> specific advice without knowing the platform and the desired workload.
Yeah. Seeing things like provisioned iops in the cloud services is a
pretty big deal. I do think it's still fairly expensive for what you
get but SSDs and competition is going to force prices down quickly
over time. For "in house" virtualized setups, you can get pretty far
with SSDs using any number of options (direct attached to the host,
iscsi etc, SAN etc).
For I/O constrained systems, I don't consider any spindle based
systems, in particular SANs, to be a good investment. Curious: I
just read your article on iscsi
(http://it.toolbox.com/blogs/database-soup/the-problem-with-iscsi-30602).
Do you still consider iscsi to be imperformant?
merlin