Message-ID: <473AD5C5.4030803@wpkg.org>
Date: Wed, 14 Nov 2007 12:02:29 +0100
From: Tomasz Chmielewski <mangoo@wpkg.org>
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Subject: Re: Strage buffer behaviour
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Denys Vlasenko wrote:

> On Sunday 11 November 2007 11:33, Tino Keitel wrote:
>> The dd command reads 100 MB from each partition two times in a row. It
>> looks like sda1 and sda2 are not bufferd (the first 4 dd runs), but
>> sda3 and sda4 are (the last 4 dd runs).
>>
>> The computer is a Mac mini with a 2,5" SATA hard disk. The first 2
>> partitions contain EFI and MacOS X, and are unused in Linux. The last 2
>> partitions are an ext3 partition for / and an LVM for the rest of the
>> sytem.
>>
>> Any hints how the dd/buffering behaviour could be explained? The system
>> was mostly idle, and the numbers are reproducible across reboots.
> 
> IIRC only mounted partitions' reads are cached.

Or, in general, those devices which kernel actually "uses" (mounted, but 
also LVM, RAID, which don't have to be mounted to get cached).


-- 
Tomasz Chmielewski
http://lists.wpkg.org
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