linux-ext4 - Re: Make huge files strictly contiguous (fallocate, bigalloc, e4defrag...)

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Message-ID: <5353DBC2.5080708@ovh.fr>
Date:	Sun, 20 Apr 2014 16:37:54 +0200
From:	Contact <neitsab@....fr>
To:	Lukáš Czerner <lczerner@...hat.com>
CC:	Theodore Ts'o <tytso@....edu>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Make huge files strictly contiguous (fallocate, bigalloc, e4defrag...)

Le ven. 18 avril 2014 10:45:03 CEST, Lukáš Czerner a écrit :
>
> The way you're using dd for this purpose is wrong. I
> said that dd can write to the file without truncating it first, but
> it's not doing it by default. You have to use 'notrunc' see man
> page. But I think that it would not have made a difference anyway.
>
Thansk, I stand corrected. I'll try it to see whether I can get better 
results with it.

> And even though you can turn off backup superblock you
> can not turn off writing group descriptors.
>
While we're at it, how can I do this? I searched the 
mkfs.ext4/mke2fs.conf/ext4/tune2fs man pages for the option to turn off 
writing backup superblock you mentioned, however the closest I found is 
tune2fs -O ^sparse_super which is part of the defaults mke2fs.conf 
options... Could you point me at it so that I can try to get this 
source of non-contiguity away?

Thanks,
-Bastien


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