On Mon, Dec 03, 2012 at 02:24:45PM +0200, Pasi Kärkkäinen wrote: > On Mon, Nov 26, 2012 at 02:27:30PM +0100, Roy Sigurd Karlsbakk wrote: > > Hi all > > > > 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? > > > > Afaik Linux md-raid raid0 and raid1 already supports T10 PI (Protection Information) and DIF (Data Integrity Fields) / DIX (Data Integrity Extensions). > > I wonder if it'd be possible to utilize this mdadm code with normal disks that don't have T10 PI support? ie. implement custom checksums in the "backend" with normal non-PI disks.. > > 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 think there are plans to implement something similar in SATA aswell in the future. > 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 Linux checksumming RAID without T10 PI disks..) -- Pasi > A couple of SAS HBAs (mpt2sas, for example) and some FC HBAs support DIF/DIX in Linux. > > The purpose of DIF/DIX is to allow passing and verifying end-to-end checksums from all the way from the applications to the disks.. and probably in more common case that'd be checksums all the way from filesystems to the disks. > > Some more links about T10 PI and DIF/DIX: > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob_plain;f=Documentation/block/data-integrity.txt;hb=HEAD > 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 > > > -- Pasi > -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
