Re: [PERFORM] Questionaire: Common WAL write rates on busy servers.

On 04/27/2017 06:34 PM, Andres Freund wrote:
> On 2017-04-27 09:31:34 -0700, Joshua D. Drake wrote:
>> On 04/27/2017 08:59 AM, Andres Freund wrote:
>>
>>>
>>> Ok, based on the, few, answers I've got so far, my experience is
>>> indeed skewed. A number of the PG users I interacted with over
>>> the last couple years had WAL write ranges somewhere in the range
>>> of 500MB/s to 2.2GB/s (max I'veseen). At that point WAL insertion
>>> became a major bottleneck, even if storage was more than fast
>>> enough to keep up. To address these we'd need some changes, but
>>> the feedback so far suggest that it's not yet a widespread
>>> issue...
>>
>> I would agree it isn't yet a widespread issue.
>
> I'm not yet sure about that actually. I suspect a large percentage
> of people with such workloads aren't lingering lots on the lists.
>

To a certain extent, this is a self-fulfilling prophecy. If you know
you'll have such a busy system, you probably do some research and
testing first, before choosing the database. If we don't perform well
enough, you pick something else. Which removes the data point.

Obviously, there are systems that start small and get busier and busier
over time. And those are the ones we see.

cheers

--
Tomas Vondra http://www.2ndQuadrant.com
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