From: Round Robinjp Subject: Re: flashing large eMMC partitions with ext4 Date: Tue, 26 Jul 2011 01:34:06 +0900 (JST) Message-ID: <20110725163406.33329.qmail@web4205.mail.ogk.yahoo.co.jp> References: <419A2628-5AF6-4B32-85B8-BE1E2B159DFA@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Cc: "linux-ext4@vger.kernel.org" To: Dilger Andreas Return-path: Received: from web4205.mail.ogk.yahoo.co.jp ([124.83.212.25]:39669 "HELO web4205.mail.ogk.yahoo.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752043Ab1GYQeI convert rfc822-to-8bit (ORCPT ); Mon, 25 Jul 2011 12:34:08 -0400 In-Reply-To: <419A2628-5AF6-4B32-85B8-BE1E2B159DFA@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 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