From: Klaus P. Pieper <kpi6288@gmail.com>
To: pgsql-admin@postgresql.org
Subject: Re: pgbench Windows outperforms Debian in Write tests while Debian is faster in SELECT only tests
Date: Mon, 29 May 2017 14:58:46 +0200
Message-ID: <030801d2d87b$4f556820$ee003860$@gmail.com> (raw)
In-Reply-To: <31836.1496045941@sss.pgh.pa.us>
References: <028501d2d84f$2f1ea840$8d5bf8c0$@gmail.com>
<31836.1496045941@sss.pgh.pa.us>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-admin>
> -----Ursprüngliche Nachricht-----
> Von: Tom Lane [mailto:tgl@sss.pgh.pa.us]
> Gesendet: Montag, 29. Mai 2017 10:19
> An: Klaus P. Pieper
> Cc: pgsql-admin@postgresql.org
> Betreff: Re: [ADMIN] pgbench Windows outperforms Debian in Write tests
> while Debian is faster in SELECT only tests
>
> "Klaus P. Pieper" < <mailto:kpi6288@gmail.com> kpi6288@gmail.com> writes:
> > How can Windows outperform Debian by a factor of 2?
>
> Are you sure you have Windows configured to fsync properly?
> Not waiting for writes to hit disk would be a really easy explanation for
a
> discrepancy of this kind.
It seems that it is indeed related to the wal_sync_method settings.
Results for 1 client read / write:
Option Windows Debian
fdatasync 340 150
fsync 125 90
open_datasync 360 160
fsync_writethrough 115 n/a
open_sync n/a 90
fsync = off 360 400
The result setting fsync=off shows that the maximum performance of the
Debian syste is above Windows.
However, with fsync=on, Windows still outperforms the Debian system with all
options.
In addition, the results on the Windows system with “fsync = off” are the
same as “wal_sync_method = open_datasync”
What does this mean?
- Is the Windows system “better” than the Debian system?
- Or is the underlying filesystem on the Windows system less safe?
- Or is the Windows system better integrated with the Hyper-V host?
The Windows systems reports that the write cache is switched on for the
virtual disk. It is however not possible to switch is off.
Thanks
Klaus
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-admin@postgresql.org
Cc: kpi6288@gmail.com
Subject: Re: pgbench Windows outperforms Debian in Write tests while Debian is faster in SELECT only tests
In-Reply-To: <030801d2d87b$4f556820$ee003860$@gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox