From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= Subject: Re: Checksumming RAID? / SCSI SAS T10 PI and DIF/DIX / T13 SATA EPP Date: Mon, 3 Dec 2012 16:09:46 +0200 Message-ID: <20121203140946.GW8912@reaktio.net> References: <14319197.21.1353936449959.JavaMail.root@zimbra> <20121203122444.GV8912@reaktio.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20121203122444.GV8912@reaktio.net> Sender: linux-raid-owner@vger.kernel.org To: Roy Sigurd Karlsbakk Cc: Linux Raid , "Martin K. Petersen" List-Id: linux-raid.ids On Mon, Dec 03, 2012 at 02:24:45PM +0200, Pasi K=E4rkk=E4inen wrote: > On Mon, Nov 26, 2012 at 02:27:30PM +0100, Roy Sigurd Karlsbakk wrote: > > Hi all > >=20 > > I see from an article at http://pages.cs.wisc.edu/~bpkroth/cs736/md= -checksums/md-checksums-paper.pdf that an implementation has been made = to allow for ZFS-like checksumming inside Linux MD. However, this code = doesn't seem to exist in any kernel trees. Does anyone know the current= status for data checksumming in MD? > >=20 >=20 > Afaik Linux md-raid raid0 and raid1 already supports T10 PI (Protecti= on Information) and DIF (Data Integrity Fields) / DIX (Data Integrity E= xtensions). >=20 > I wonder if it'd be possible to utilize this mdadm code with normal d= isks that don't have T10 PI support? ie. implement custom checksums in = the "backend" with normal non-PI disks.. >=20 > T10 PI and DIF/DIX is a SCSI/SAS feature, so it's mostly available in= new(ish) enterprise SAS disks and it's not available in SATA.. but I t= hink there are plans to implement something similar in SATA aswell in t= he future. >=20 Now I remember.. it's the SATA T13 "External Path Protection" (EPP). (Added CC to Martin in the case he has some thoughts about generic Linu= x checksumming RAID without T10 PI disks..) -- Pasi > A couple of SAS HBAs (mpt2sas, for example) and some FC HBAs support = DIF/DIX in Linux. >=20 > The purpose of DIF/DIX is to allow passing and verifying end-to-end c= hecksums from all the way from the applications to the disks.. and prob= ably in more common case that'd be checksums all the way from filesyste= ms to the disks. >=20 > Some more links about T10 PI and DIF/DIX: > http://git.kernel.org/?p=3Dlinux/kernel/git/torvalds/linux.git;a=3Dbl= ob_plain;f=3DDocumentation/block/data-integrity.txt;hb=3DHEAD > https://oss.oracle.com/~mkp/docs/dix.pdf > https://oss.oracle.com/~mkp/docs/osd2008-data-integrity.pdf > https://oss.oracle.com/~mkp/docs/ols2008-petersen.pdf > https://oss.oracle.com/~mkp/docs/ppdc.pdf >=20 >=20 > -- Pasi >=20 -- 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