On Fri, 3 Jul 2015 12:35:07 +0200
Jean-Gérard Pailloncy <jg.pailloncy@adnow.fr> wrote:
>
> I work on a project that collects geolocalized data.
> All data will be in PostgreSQL / PostGIS.
>
> The small PostgreSQL databases will be on Linux guests on VMWare hosts.
>
> The size of the main database will grow by 50 TB / year, 500 M row / day.
> For the largest one, we plan to test different options.
> One of them is to stay with Linux on WMWare.
> Outside the questions about schema, sharding, I would appreciate if some of you have informations, benchmarks,
storiesabout big PostgreSQL databases on Linux guests on VMWare hosts.
The place I'm working now did a feasibility study about installing
their primary app on vmware instead of directly onto the hardware.
Their conclusion was that the app would be about 25% slower running
on VMWare. The app is very database-centric. However, I wasn't
involved in the tests, can't vouche for the quality of the testing,
and there _are_ other pieces involved than the database.
That being said, I've used PostgreSQL on VMs quite a bit. It does
seem slower, but I've never actually benchmarked it. And it's never
seemed slower enough for me to complain much.
The concern I have about running a large database on a VM (especially
since you're asking about performance) is not he VM itself, but all
the baggage that inevitably comes with it ... oversubscribed hosts,
terrible, cheap SANs, poor administration leading to bad configuration,
and yet another layer of obscurity preventing you from figuring out
why things are slow. In my experience, you _will_ get all of these,
because once you're on a VM, the admins will be pressured to host
more and more VMs on the existing hardware and/or add capacity at
minimal cost.
There's nothing like a VM where you never know what the performance
will be because you never know when some other VMs (completely unrelated
to you and/or your work) will saturate the IO with some ridiculous
grep recursive command or something.
--
Bill Moran
