From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roy Sigurd Karlsbakk Subject: Re: Suboptimal raid6 linear read speed Date: Sat, 19 Jan 2013 14:21:59 +0100 (CET) Message-ID: <20597456.6.1358601718986.JavaMail.root@zimbra> References: <50F9D32F.7090606@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <50F9D32F.7090606@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: stan@hardwarefreak.com Cc: linux-raid@vger.kernel.org, Mikael Abrahamsson List-Id: linux-raid.ids > >> The probability of a URE during rebuild increases with the number > >> and > >> size of the source drives being read to rebuild the failed drive. > >> Thus > >> the probability of encountering a URE in the 1:1 drive scenario is > >> extremely low, close to zero if you believe manufacturer specs. > > > > For a 2TB drive and BER 10^-14 (common for non-enterprise drives), > > the > > probability is 1/6 of a single URE for a read of the entire drive. >=20 > If my math is correct, with a URE rate of 10E14, that's one URE for > every ~12.5TB read. So theoretically one would have to read the entir= e > 2TB drive more than 6 times before hitting the first URE. So it seems > unlikely that one would hit a URE during a mirror rebuild with such a > 2TB drive. ok, perhaps, maybe, but then it's 17% chance of losing data after a mir= ror or raid-5 rebuild with 2TB drives, or the double of that if using 4= TB drives. That's not very amusing=E2=80=A6 Vennlige hilsener / Best regards roy -- Roy Sigurd Karlsbakk (+47) 98013356 roy@karlsbakk.net http://blogg.karlsbakk.net/ GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt.= Det er et element=C3=A6rt imperativ for alle pedagoger =C3=A5 unng=C3=A5= eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilf= eller eksisterer adekvate og relevante synonymer p=C3=A5 norsk. -- 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