linux-ext4 - Re: flashing large eMMC partitions with ext4

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Date:	Tue, 26 Jul 2011 01:34:06 +0900 (JST)
From:	Round Robinjp <roundrobinjp@...oo.co.jp>
To:	Dilger Andreas <aedilger@...il.com>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: flashing large eMMC partitions with ext4

Many Thanks for the reply.

In both the ways you have shown, the eMMC device needs
to be zeroed in advance. But so far as I know, writing
4G bytes of zeros and writing 4G bytes of real data has
no difference. So this does not solve the problem.
Please correct me if I am wrong.
Any other options?

Thanks
Robin


--- Andreas Dilger  wrote:
> If you can wipe the MMC device to be all-zero efficiently, then you can format it quickly with "mke2fs -E lazy_itable_init,lazy_journal_init ..." and restore from a tarball.
> 
> Alternately, Lukas recently added support for QCOW2 sparse image format, and it should be possible to restore this to the device efficiently, if it is zeroed in advance. I don't know if his code skips all-zero blocks in the image, but that should be possible to add fairly easily. 
> 
> Cheers, Andreas
> 
> On 2011-07-22, at 9:49 AM, Round Robinjp <roundrobinjp@...oo.co.jp> wrote:
> 
> > Hi
> > 
> > I have a question regarding making ext4 image for
> > large eMMC partition.
> > 
> > We have a 4G partition in our embedded device
> > in which we want to use ext4 filesystem.
> > But for that we have to create a 4G image.
> > flashing this 4G image to the eMMC takes a long
> > time. Is there any way to reduce this time?
> > 
> > For vfat, you can truncate the image leaving only
> > non zero-filled blocks which makes the image very
> > short and the time for flashing is reduced.
> > Is something similar to that possible for ext4?
> > 
> > Thanks
> > Robin
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