From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roy Sigurd Karlsbakk Subject: Re: Checksumming RAID? Date: Wed, 28 Nov 2012 11:58:01 +0100 (CET) Message-ID: <32402494.9.1354100281894.JavaMail.root@zimbra> References: <50B52740.5000201@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <50B52740.5000201@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: stan@hardwarefreak.com Cc: Linux Raid , Bernd Schubert , David Brown List-Id: linux-raid.ids > > To do checksumming (and in particular, recovery), requires higher > > level > > knowledge of the data. The filesystem can track when it writes a > > file, > > and update metadata (including, if desired, a data checksum) once i= t > > knows the file is correctly stored. But I don't think it can > > sensibly > > be done at the block device level - the recovery procedure doesn't > > know > > what is old data, what is new data, or which bit is important to th= e > > filesystem. > > > > So I think it can make sense to use a filesystem like ZFS or BTRFS > > that > > can do checksumming - that is a reasonable level to add the > > checksum. >=20 > You'll see CRC in XFS in the future as well. Some of the foundation i= s > already laid to allow it, but IIRC it requires an on disk format > change > for full implementation. On disk format changes are a big deal and ar= e > taken with great care. IIRC XFS has only seen one or two in 18 years. I'm afraid that won't help much either, since it'll only allow for *det= ecting* the errors, and not *fixing* them (as with ZFS and Btrfs). Or p= erhaps if XFS can integrate with MD somehow? 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