From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.nokia.com ([192.100.122.233] helo=mgw-mx06.nokia.com) by bombadil.infradead.org with esmtps (Exim 4.68 #1 (Red Hat Linux)) id 1KO59r-0007Kf-2J for linux-mtd@lists.infradead.org; Wed, 30 Jul 2008 06:27:35 +0000 Subject: Re: Deep thinking about the Wear-leveling mothed From: Artem Bityutskiy To: xiaochuan-xu In-Reply-To: <1217327479.2812.24.camel@localhost.localdomain> References: <1217327479.2812.24.camel@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Date: Wed, 30 Jul 2008 09:22:53 +0300 Message-Id: <1217398973.9048.7.camel@sauron> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Cc: linux-mtd Reply-To: dedekind@infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi, On Tue, 2008-07-29 at 18:31 +0800, xiaochuan-xu wrote: > 2. Do we really need wear-leveling when the oldest PEB is far from the > upper limit of reliable erasure?=20 > the answer is NO!=20 I would not be so sure. When UBI looses an erase counter because of an unclean reboot, it assigns average erase counter to that eraseblock. This works fine because UBI maintains a reasonably small Max-Min difference. Also, I am not sure it is save to erase one eraseblock several million times and do not erase neighbor eraseblocks. There are "radiation" effects in some flashes, when unused eraseblocks slowly "rot" when their neighbor eraseblocks are used a lot. --=20 Best regards, Artem Bityutskiy (=D0=91=D0=B8=D1=82=D1=8E=D1=86=D0=BA=D0=B8=D0=B9 =D0=90= =D1=80=D1=82=D1=91=D0=BC)