On 09/18/2014 03:09 PM, Mkrtchyan, Tigran wrote:
>
> ----- Original Message -----
>> From: "Josh Berkus" <josh@agliodbs.com>
>> To: pgsql-performance@postgresql.org
>> Sent: Thursday, September 18, 2014 7:54:24 PM
>> Subject: Re: [PERFORM] postgres 9.3 vs. 9.4
>>
>> On 09/18/2014 08:09 AM, Mkrtchyan, Tigran wrote:
>>>>> 9.4beta2:
>>>>> ...
>>>>>
>>>>>>> 0.957854 END;
>>>>>>>
>>>>> Looks like IO.
>>> Postgres internal IO? May be. We get 600MB/s on this SSDs.
>> While it's possible that this is a Postgres issue, my first thought is
>> that the two SSDs are not actually identical. The 9.4 one may either
>> have a fault, or may be mostly full and heavily fragmented. Or the Dell
>> PCIe card may have an issue.
>
> We have tested both SSDs and they have identical IO characteristics and
> as I already mentioned, both databases are fresh, including filesystem.
>
>> You are using "scale 1" which is a < 1MB database, and one client and 1
>> thread, which is an interesting test I wouldn't necessarily have done
>> myself. I'll throw the same test on one of my machines and see how it does.
> this scenario corresponds to our use case. We need a high transaction rate
> per for a single client. Currently I can get only ~1500 tps. Unfortunately,
> posgtress does not tell me where the bottleneck is. Is this is defensively
> not the disk IO.
>
>
>
This is when you dig out tools like perf, maybe.
cheers
andrew