From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roy Sigurd Karlsbakk Subject: Re: Checksumming RAID? Date: Tue, 27 Nov 2012 14:56:34 +0100 (CET) Message-ID: <25425956.18.1354024591879.JavaMail.root@zimbra> References: <50B4BE27.1050101@hesbynett.no> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <50B4BE27.1050101@hesbynett.no> Sender: linux-raid-owner@vger.kernel.org To: David Brown Cc: Linux Raid , Bernd Schubert List-Id: linux-raid.ids > > If this system is running RAID-6, recovery should be possible to > > check both parity chunks, right? >=20 > Yes, of course. (And if anyone ever needs it, it is possible to exten= d > raid6 to 3 parity chunks. I've done the maths, but it is not > implemented - there doesn't seem to be a big need for it.) But - agai= n > referring back to Neil's blog - if the low-level raid spots a > consistency error, it still cannot correct it reliably even with 2 > parity chunks, and should pass on a read error to the higher level > raid. > Using raid6 at the low level would let you do a good consistency chec= k > even in the case of a failed drive (or a known read error on a drive) > - > or two simultaneous undetected read errors. And raid6 on the higher > level raid would let you correct such errors, even when there are > other > errors around. You'd soon reach the point where it is more likely for > your disks to spontaneously turn into a bowl of petunias than for rea= d > errors to be undetected or unrecoverable. That would be nice. So what should be done here in the first place, is = to change the code to allow parity data to be read and calculated also = on reads? 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