linux-kernel - Re: Fwd: ext2/3 create large filesystem takes too much time; solutions

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Date:	Sat, 16 Sep 2006 18:05:07 +0300
From:	"Pavel Mironchik" <tibor0@...il.com>
To:	"Jan Kara" <jack@...e.cz>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Fwd: ext2/3 create large filesystem takes too much time; solutions

Hi Jan,

Probably you are right, but there are lot of competitive filesystems
(reiser,xfs) that do not require such period on creation. I hope at
least Ext4 users will not suffer about that.

Pavel.

On 9/15/06, Jan Kara <jack@...e.cz> wrote:
>   Hello,
>
> > Ext2/3 does erase of inode tables, when do creation of new systems.
> > This is very very long operation when the target file system volume is more
> > than
> > 2Tb. Other filesystem are not affected by such huge delay on creation of
> > filesystem. My concern was to improve design of ext3 to decrease time
> > consuption of creation large ext3 volumes on storage servers.
> > In general to solve problem, we should defer job of cleaning nodes to
> > kernel. In e2fsprogs there is LAZY_BG options but it  just avoids doing
> > erase of inodes only.
> >
> > I see several solutions for that problem:
> > 1) Add special bitmaps into fs header (inode groups descriptors?).
> > By looking at those bitmaps kernel could determine if inode is not cleaned,
> > and
> > that inode will be propertly initialized.
> > 2) Add special identifiers into inodes. If super block id != inode id
> > -> inode is dirty
> > and should be cleaned in kernel, where super block id is generated on
> > creation stage.
>   Hmm, I don't know but how often do you need to create so big
> filesystems? My feeling is that one can usually afford to spend some
> time with a creation of a filesystem (and it is better to spend it
> during creation than to add complexity to the run-time code). Also
> having inodes zeroed out is more robust when filesystem is corrupted or
> some other nasty thing happens... Just my 2 cents :)
>
>                                                                 Honza
> --
> Jan Kara <jack@...e.cz>
> SuSE CR Labs
>
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