From: Yeb Havinga <yebhavinga@gmail.com>
To: Hannu Krosing <hannu@2ndquadrant.com>
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Greg Smith <greg@2ndquadrant.com>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Testing Sandforce SSD
Date: Tue, 03 Aug 2010 13:19:57 +0200
Message-ID: <4C57FB5D.1020006@gmail.com> (raw)
In-Reply-To: <1280826522.14579.66.camel@hvost>
References: <4C4A9452.9070100@gmail.com>
<4C4B1F84.5030306@2ndquadrant.com>
<4C4B4B41.7000800@2ndquadrant.com>
<4C52E957.8020304@gmail.com>
<AANLkTinNX63EsRtNjtKeeygymWjH8VA3EWwxBzXGCy0=@mail.gmail.com>
<4C56DD8B.6050303@gmail.com>
<4C5744F5.3020805@agliodbs.com>
<4C575DCF.3050700@2ndquadrant.com>
<AANLkTikQ=CUSoRy+MxYA2TAfk2hdipA4Uz_qYXyu+yhR@mail.gmail.com>
<4C57D5FD.9040306@gmail.com>
<1280826522.14579.66.camel@hvost>
Hannu Krosing wrote:
> Did it fit in shared_buffers, or system cache ?
>
Database was ~5GB, server has 16GB, shared buffers was set to 1920MB.
> I first noticed this several years ago, when doing a COPY to a large
> table with indexes took noticably longer (2-3 times longer) when the
> indexes were in system cache than when they were in shared_buffers.
>
I read this as a hint: try increasing shared_buffers. I'll redo the
pgbench run with increased shared_buffers.
>> so the test is actually how fast the ssd can capture
>> sequential WAL writes and fsync without barriers, mixed with an
>> occasional checkpoint with random write IO on another partition). Since
>> the WAL writing is the same for both block_size setups, I decided to
>> compare random writes to a file of 5GB with Oracle's Orion tool:
>>
>
> Are you sure that you are not writing full WAL pages ?
>
I'm not sure I understand this question.
> Do you have any stats on how much WAL is written for 8kb and 4kb test
> cases ?
>
Would some iostat -xk 1 for each partition suffice?
> And for other disk i/o during the tests ?
>
Not existent.
regards,
Yeb Havinga
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-performance@postgresql.org
Cc: yebhavinga@gmail.com, hannu@2ndquadrant.com, scott.marlowe@gmail.com, greg@2ndquadrant.com, josh@agliodbs.com
Subject: Re: Testing Sandforce SSD
In-Reply-To: <4C57FB5D.1020006@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