Check the thread started by Matthias within last week. On Sun, Sep 20, 2009 at 12:36 PM, John Robinson <john.robinson@xxxxxxxxxxxxxxxx> wrote: > On 19/09/2009 17:10, Greg Freemyer wrote: > [...] >> >> I don't know how specifically, but it also seems to me the mdraid >> stack could add to currently poor data integrity process even in the >> absence of a supporting scsi subsystem. Maybe by pulling out the >> integrity checksum / crc info and putting it on yet another disk, or >> mixing it in with the parity calculation. >> >> Specifically you could steal the second parity stripe from a raid 6 >> setup and replace it with this end-to-end data integrity checksum / >> crc. The checksum / crc is much smaller than the original data so the >> one integrity disk should support a reasonable number of data disks. >> Obviously this would not be one of the formal raid levels, but that >> doesn't mean its not useful. > > I vaguely remember someone here was prototyping/developing a device mapper > thingy which added checksumming/integrity to simulate high-end RAID cards > adding a checksum to each 512-byte sector by using 520- or 528-byte sectors > on their component discs. I don't remember the details, but what I have in > mind was something along the lines of using an extra sector on the > underlying device per 64 sectors or so. There wouldn't be too heavy an > overhead on small reads - we do readahead anyway - and it would make small > writes even more painful than they are already, but shouldn't significantly > reduce throughput on large (chunk size) reads and writes. I'd use it. > > Cheers, > > John. > -- > 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 > -- Majed B. -- 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
