From: Dmitry Koterov <dmitry@koterov.ru>
To: pgsql-performance@postgresql.org
Subject: Are random writes optimized sequentially by Linux kernel?
Date: Wed, 7 Jan 2009 21:39:12 +0300
Message-ID: <d7df81620901071039s3c8cafd8x79a0886a8bca605@mail.gmail.com> (raw)
Hello.
Suppose I perform 1000 RANDOM writes into a file. These writes are saved
into Linux writeback buffer and are flushed to the disc asynchronously,
that's OK.
The question is: will physical writes be performed later in the sequence of
physical SECTOR position on the disc (minimizing head seeking)? Or Linux
background writer knows nothing about physical on-disc placement and flushes
data in order it is saved in the RAM?
E.g., if I write in the application:
a) block 835
b) block 136
c) block 956
d) block 549
e) block 942
dows the Linux background writer save flush them e.g. in physical order "136
- 549 - 835 - 942 - 956" or not?
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To: pgsql-performance@postgresql.org
Cc: dmitry@koterov.ru
Subject: Re: Are random writes optimized sequentially by Linux kernel?
In-Reply-To: <d7df81620901071039s3c8cafd8x79a0886a8bca605@mail.gmail.com>
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