From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga01.intel.com ([192.55.52.88]) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1SIjpe-0003UC-Li for linux-mtd@lists.infradead.org; Fri, 13 Apr 2012 16:58:47 +0000 Message-ID: <1334336505.13160.19.camel@sauron.fi.intel.com> Subject: RE: Unstable bits and JFFS2 From: Artem Bityutskiy To: Atlant Schmidt Date: Fri, 13 Apr 2012 20:01:45 +0300 In-Reply-To: <0A40042D85E7C84DB443060EC44B3FD3351F9CADBE@dekaexchange07.deka.local> References: <0A40042D85E7C84DB443060EC44B3FD3351F9CAD87@dekaexchange07.deka.local> <1334334462.13160.10.camel@sauron.fi.intel.com> <0A40042D85E7C84DB443060EC44B3FD3351F9CADBE@dekaexchange07.deka.local> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-UDDrcLZ1gTDvKVmIGNmK" Mime-Version: 1.0 Cc: 'Matej Kupljen' , Brian Norris , linux-mtd Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-UDDrcLZ1gTDvKVmIGNmK Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2012-04-13 at 12:40 -0400, Atlant Schmidt wrote: > Artem: >=20 > > Yeah, thanks for correcting. Yeah, read/write-disturb may make bits > > to become unstable, but we assume this is a slow process which will > > gradually make more and more bits flip and ECC will take care of > > that. So I think Matej can exclude this. >=20 > Unfortunately, ECC can only fix those PEBs that > are actually read. If one of the PEBs in your > filesystem is being used entirely to contain > obscure data that only gets read once in a > blue moon (i.e., very rarely), then multiple > read-/write-disturbs can hit accumulate in > that PEB and when it is finally read, it may > already contains too many errors to be > corrected by the ECC. >=20 > We've seen this exact scenario occur with the > current UBI/UBIfs and will be implementing a > userland "scrubbing" system to ensure that > every PEB gets read at least once in a while > (e.g., weekly or whatever interval seems right). This is right, people should have a user-space app which periodically reads all /dev/ubiX_Y. Care to send a patch against mtd-www with some explantion of this issue and extend the unstable bits issue? But in Matej's case I do not believe he is testing long enough to hit this scenario. But everything is possible of course. --=20 Best Regards, Artem Bityutskiy --=-UDDrcLZ1gTDvKVmIGNmK Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAABAgAGBQJPiFv5AAoJECmIfjd9wqK0xpQP/2wEX2rCP5yIAxQHXABO6+0o zzlYZQq3TyQ+PuYpA+WVpk0NFVF5zXhYWO54eGCyxTXcnTl6Q+ze+UsL+l7gjDfG 6KU4ZaB1a3+5sCV5hDbeeW3crH2o6O1+OdceA38T30yRj5qCbJyJEkTkfwc8IlQN rXf7nI8px69pRir7DS4Bv0Ihsuxqcmh+e2mmIPZ9aQMBjGQ5HlbTzVosr6L6zEeF quK8/QgAqG42iSpQ1lmCaYTHGtz1Idkhu9qezrMY0sxoADA/cOnWgf7coGz7WFU6 k+P8DIv1wZLY5E72ws3Wh8C943HMfVrsODncltG62GXlwnJIP7W2INNXSYbwr+k5 4MwA4HCwXgGqAfrwcRyEyZoTXekFoSb+Hi0CXxcCailGvuI45DyKL6eqwOS6hjOh TQfvtTvVzBKh5HHQjyjAXS5CiDWuH0QL4syz11MDkxU4S66rY1uYDNL1n4UzIUO5 hKAFTpyFJbhuCOvUR8vzyGokHTViQ/xFvuond/4BulQ5M42DkvRdtGhIX6qHDSLV 55m/6MpBrRN+oPx7PPmBWTH6G1FoeWr+gvSFb2gJt+yKuMKrdQet6XRrQsOhFWfK 346ChZD+uADg3o78km2kRs49KK5r4bVrgAcna7GhpVUKYKwRzRwKSOFnAHvIMU5Q 0AdZv+wSnpvVnbXuSapP =3iKP -----END PGP SIGNATURE----- --=-UDDrcLZ1gTDvKVmIGNmK--