From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from risingsoftware01.propagation.net ([66.221.33.65]) by bombadil.infradead.org with esmtps (Exim 4.68 #1 (Red Hat Linux)) id 1JxzIL-0004rD-Ip for linux-mtd@lists.infradead.org; Mon, 19 May 2008 06:56:29 +0000 Date: Mon, 19 May 2008 16:56:23 +1000 From: Hamish Moffatt To: Artem Bityutskiy Subject: Re: ext2 for read-only file system on UBI Message-ID: <20080519065623.GA17246@cloud.net.au> References: <20080519062149.GA16462@cloud.net.au> <1211179073.27243.22.camel@sauron> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1211179073.27243.22.camel@sauron> Cc: linux-mtd@lists.infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Artem, thanks for your response. On Mon, May 19, 2008 at 09:37:53AM +0300, Artem Bityutskiy wrote: > On Mon, 2008-05-19 at 16:21 +1000, Hamish Moffatt wrote: > > My embedded device has a read-only root file system which is only > > replaced by writing a whole image (dd, flashcp, ubiupdatevol etc). > > > > Using gluebi and mtdblock, I think I can put a traditional block file > > system (eg ext2) on top of NAND flash. What are the disadvantages of > > this? (For the read-only application only.) > > For read-only it should be ok, although I am not sure mtdblock will like > non power of 2 eraseblock sizes. But this should be trivial to fix. > > > Background: I've got older hardware which uses ext2 on top of compact > > flash in IDE mode, and new hardware which has replaced the compact flash > > with NAND. I'd like to share an ext2 image between the two if possible. > > Should be possible for R/O. Different sizes of eraseblocks may add extra > work though. > > > The read-write file systems use ubifs. I'm only considering this for the > > read-only volumes. One obvious disadvantage is lack of compression. Are > > there others? Do I still get the reliability of ubi? > > No, should be fine. Well, you'll still have WL across whole NAND chip, > yes. You'll still have bit-flip handling. So, is there a benefit to Nancy's proposed ubi block layer as opposed to gluebi + mtdblock? ( http://lists.infradead.org/pipermail/linux-mtd/2008-May/021609.html ) regards Hamish -- Hamish Moffatt VK3SB