Re: Why we are going to have to go DirectIO

On 12/04/2013 07:30 PM, Joshua D. Drake wrote:
>
> On 12/04/2013 07:32 AM, Stefan Kaltenbrunner wrote:
>>
>> On 12/04/2013 04:30 PM, Peter Eisentraut wrote:
>>> On 12/4/13, 2:14 AM, Stefan Kaltenbrunner wrote:
>>>> running a
>>>> few kvm instances that get bootstrapped automatically is something that
>>>> is a solved problem.
>>>
>>> Is it sound to run performance tests on kvm?
>>
>> as sounds as on any other platform imho, the performance characteristics
>> will differ between bare metal or other virtualisation platforms but the
>> future is virtual and that is what a lot of stuff runs on...
>
> In actuality you need both. We need to know what the kernel is going to
> do on bare metal. For example, 3.2 to 3.8 are total crap for random IO
> access. We will only catch that properly from bare metal tests or at
> least, we will only catch it easily on bare metal tests.
>
> If we know the standard bare metal tests are working then the next step
> up would be to test virtual.
>
> BTW: Virtualization is only one future and it is still a long way off
> from serving the needs that bare metal serves at the same level
> (speaking PostgreSQL specifically).

we need to get that off the ground - and whatever makes it easier to get
off the ground will help. and if we solve the automation for
virtualisation, bare metal is just a small step away (or the other way
round). Getting comparable performance levels between either different
postgresql versions (or patches) or different operating systems with
various workloads is probably more valuable now that getting absolute
peak performance levels under specific tests long term.

Stefan