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

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Date:	Fri, 22 Jul 2011 10:35:20 -0600
From:	Andreas Dilger <aedilger@...il.com>
To:	Round Robinjp <roundrobinjp@...oo.co.jp>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: flashing large eMMC partitions with ext4

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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