From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.nokia.com ([192.100.122.230] helo=mgw-mx03.nokia.com) by bombadil.infradead.org with esmtps (Exim 4.69 #1 (Red Hat Linux)) id 1NHjqC-0000q1-97 for linux-mtd@lists.infradead.org; Mon, 07 Dec 2009 20:05:57 +0000 Message-ID: <4B1D600A.10507@nokia.com> Date: Mon, 07 Dec 2009 22:05:30 +0200 From: Adrian Hunter MIME-Version: 1.0 To: twebb Subject: Re: ubifs wear leveling across entire device References: <4B18F300.7080006@nokia.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "linux-mtd@lists.infradead.org" List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , twebb wrote: >>> I'm confused about how wear leveling occurs across the entire device >>> in the following example. Could someone help me understand what I'm >>> missing? >>> >>> 4 GiB flash device (nand MLC): >>> 4 MTD partitions defined: >>> 0 - "p1" - 0x00000000 - 0x00800000 >>> 1 - "p2" - 0x00800000 - 0x10000000 >>> 2 - "p3" - 0x10000000 - 0x80000000 >>> 3 - "p4" - 0x80000000 - 0x100000000 >>> >>> kernel args specify 3 ubi volumes: >>> ubi.mtd=p1 ubi.mtd=p2 ubi.mtd=p3 >>> (p4 is reserved and no volumes or filesystems sit on top of it) >> That is 3 UBI devices not 3 UBI volumes >> > > Excuse me. I'm new to using UBI and UBIFS and am not completely > familiar with the terminology. I think what I described in the > example is 3 UBI devices, with a single volume associated with each > device. I had neglected to show that each UBI device had a single > volume. > > Maybe there's a better way to word my question. Does UBI wear > leveling occur independently across each MTD device (p1, p2, and p3 > only in example above) or does it somehow occur over the entire > physical device (p1-p4 inclusive)? > > I'm trying to understand this so I can determine how to partition the > physical device to provide the best wear leveling, while still > allowing a portion of the physical device (p4) to exist outside of any > UBI device or volume. Wear-levelling occurs within a single UBI device which is generally a single MTD partition. You need 1 MTD partition and 1 UBI device with 3 volumes. Make the 3 volumes total less than the whole UBI device and you can add a 4th volume later.