From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Murphy Subject: Re: Chances of silent errors? Date: Tue, 22 Jan 2013 09:28:55 -0700 Message-ID: <83E6A21C-E6EF-4437-A265-67839431EA4E@colorremedies.com> References: <24463267.2.1358852138003.JavaMail.root@zimbra> Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <24463267.2.1358852138003.JavaMail.root@zimbra> Sender: linux-raid-owner@vger.kernel.org To: Roy Sigurd Karlsbakk Cc: linux-raid Raid List-Id: linux-raid.ids On Jan 22, 2013, at 3:55 AM, Roy Sigurd Karlsbakk w= rote: >> Coming from the zfs world, I've heard a few talk about the chances o= f >> "silent errors", meaning the checksum on the drives match, but the >> data being bad because of matching checksum (aka collisions). Does >> anyone in here know the relative chance of something like that >> happening with the checksums of current harddisks? Is the 1:10^14 or >> 1:10^15 chances for a URE in regard to this, or is that when the dri= ve >> reports an error, or those two combined? >=20 > A follow-up here. I see drive manufacturers report the chance of an U= RE is 1:10^14 for desktop drives, 1:10^15 for 7k2RPM enterprise drives = and 1:10^16 for 10k and 15k enterprise drives (or most do). I was under= the impression that "nearline" / 7k2 enterprise drives were the same = thing as desktop drives, only with a slightly different firmware (TLER = and friends =3D> don't do anything as stupid as going into "deep recove= ry mode" like some desktop drives do). >=20 > Any idea if there's a real difference between the hardware on enterpr= ise and desktop 7k2 drives? Is this 10-fold difference between error ra= tes real, or is it just marketing? SNIA has said there are differences in ECC between consumer SATA, nearl= ine SATA, and enterprise SAS for some time. They also distinguish quite= a few other differences that aren't ECC related, but they don't discus= s error rates directly. And this is old information=85 http://www.snia.org/sites/default/education/tutorials/2007/spring/stora= ge/Desktop_Nearline_Deltas_by_Design.pdf Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html