From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: [RFE] Please, add optional RAID1 feature (= chunk checksums) to make it more robust Date: Wed, 18 Jul 2012 21:15:37 +1000 Message-ID: <20120718211537.516b574f@notabene.brown> References: <17025a94-1999-4619-b23d-7460946c2f85@zmail15.collab.prod.int.phx2.redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/5beFG_lWh1gHj8ra3DZOv1e"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Jaromir Capik Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/5beFG_lWh1gHj8ra3DZOv1e Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 18 Jul 2012 07:01:48 -0400 (EDT) Jaromir Capik wrote: > Hello. >=20 > I'd like to ask you to implement the following ... >=20 > The current RAID1 solution is not robust enough to protect the data > against random data corruptions. Such corruptions usually happen > when an unreadable sector is found by the drive's electronics > and when the drive's trying to reallocate the sector to the spare area. > There's no guarantee that the reallocated data will always match > the original stored data since the drive sometimes can't read the data > correctly even with several retries. That unfortunately completely masks > the issue, because the sector can be read by the OS without problems > even if it doesn't contain correct data. If a drive ever lets you read incorrect data rather than giving you an error indication, then the drive is broken by design. Don't use drives that do that. > Would it be possible > to implement chunk checksums to avoid such data corruptions? No. NeilBrown > If a corrupted chunk is encountered, it would be taken from the second > drive and immediately synced back. This would have a small performance > and capacity impact (1 sector per chunk to minimize performance impact > caused by unaligned granularity =3D 0.78% of the capacity with 64k chunks= ). >=20 > Please, let me know if you find my request reasonable or not. >=20 > Thanks in advance. >=20 > Regards, > Jaromir. >=20 > -- > Jaromir Capik > Red Hat Czech, s.r.o. > Software Engineer / BaseOS >=20 > Email: jcapik@redhat.com > Web: www.cz.redhat.com > Red Hat Czech s.r.o., Purkynova 99/71, 612 45, Brno, Czech Republic > IC: 27690016=20 >=20 >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --Sig_/5beFG_lWh1gHj8ra3DZOv1e Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBUAaa2Tnsnt1WYoG5AQK+IBAAnkgKoKHGxXyWJJELRUGAwlPxe1rA5cKu gG22bAXFTEUi3DnhYZv/2IkuFRlPH9Ghqk6H/RVrOwLyzmZX7UxaStSVw5IkOxT+ aMfpfRd9AMLb0p+uKFUi8WnZxjo0y0/NnBs3nfjrkupLSyEqDZPi+nge/2JrKSgJ r0YnrYPBx9h3iI1+o3E8uQQUcCDYtfHfFMILboxFkoEJxjkTdT/aS8DhN6q040sU Jc+bgvP0iaGNuAvIx+jrMC4LkoEMCE4bs6Lywm2x0Q0/+YHnnaMzGiBR6uqFHtOe +t8T6aSHLrlRIX9710/YbTg+ZvSXGKrZG2SafIV7mo+Tqy/eN4cjDVOj6taaQC+p kC/F4KVWw0TWwpePREE9vyZMmQpARji6xOiNsAt8fAr2pOJk/R7cUpFZugkm9eGj miTavZlOKqf9T6lME1JiRsDMr3ytpCcv3yg3BvbrZzHIDycoOBFi0npMW6h1MKr1 9Dw+ISD5e4Pu8XBXYBrVMN+3w7RzD6zC1D2sz+OVYAoeUt/NqDXkXUwXK9oc3DE3 dHhvFGKE7DkpQ12Tog6SUbPLUnNTLNsX7cFKYg0mfWnTUMIYj7Ce8OuaT7QO86Y4 6iYLCMnUuK72mlbHQno8BDIprRAoeugOn6AtmVYORBST2JnFdMatb/hDs60VNPPm tFSxkOSeqzE= =rUMN -----END PGP SIGNATURE----- --Sig_/5beFG_lWh1gHj8ra3DZOv1e--