Date: Thu, 18 Sep 2014 21:09:24 +0200 (CEST)
From: "Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>
To: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-performance@postgresql.org
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Subject: Re: postgres 9.3 vs. 9.4
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----- 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.


Thanks for the help,
Tigran.

> 
> --
> Josh Berkus
> PostgreSQL Experts Inc.
> http://pgexperts.com
> 
> 
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