Message-ID: <5293B0B9.1060200@vmware.com>
Date: Mon, 25 Nov 2013 22:19:05 +0200
From: Heikki Linnakangas <hlinnakangas@vmware.com>
Organization: VMware
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To: Lee Nguyen <leemobile@gmail.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Postgresql in a Virtual Machine
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On 25.11.2013 22:01, 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.
>
> 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.
>
> Why shouldn't we run Postgres in a VM?  What are the downsides? Does anyone
> have any metrics or benchmarks with the latest Postgres?

I've also heard people say that they've seen PostgreSQL to perform worse 
in a VM. In the performance testing that we've done in VMware, though, 
we haven't seen any big impact. So I guess the answer is that it depends 
on the specific configuration of CPU, memory, disks and the software. 
Synchronous replication is likely going to be the biggest bottleneck by 
far, unless it's mostly read-only. I don't know if virtualization will 
have a measurable impact on network latency, which is what matters for 
synchronous replication.

So, I'd suggest that you try it yourself, and see how it performs. And 
please report back to the list, I'd also love to see some numbers!

- Heikki


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