Loic, As Benoit points out, Mojette uses discrete geometry rather than algebra, so simple XOR is all that is needed. Benoit, Microsoft's paper states that their [12,2,2] LRC provides better availability than 3x replication with 1.33x efficiency. 1.5x is certainly a good number. I'm just pointing out that better efficiency can be had without losing availibity. All the best, Paul On 6/16/2013 02:31 PM Loic Dachary wrote: > Hi Benoît, > > From the ( naïve ) point of view of engineering, performances are > important. The recent works of James Plank ( cc'ed ) greatly improved them > and I'm looking forward to the next version of jerasure > ( http://web.eecs.utk.edu/~plank/plank/papers/CS-08-627.html ). Rozofs > Mojette Transform implementation > ( https://github.com/rozofs/rozofs/blob/master/rozofs/common/transform.h & > https://github.com/rozofs/rozofs/blob/master/rozofs/common/transform.cc ) > does not seem to make use of SIMD. Is it because the performances are good > enough to not require them ? > > Cheers > > On 06/16/2013 09:51 PM, Benoît Parrein wrote: > > Paul Von-Stamwitz <PVonStamwitz <at> us.fujitsu.com> writes: > > > > Hi Paul, > > > >> > >> Loic, I know nothing about Mojette Transforms. From what little I > gleaned, > > it might be good for repair > >> (needing only a subset of chunks within a range to recalculate a > missing > > chunk) but I'm worried about the > >> storage efficiency. RozoFS claims 1.5x. I'd like to do better than that. > >> > >> All the best, > >> Paul > >> > > > > If you want to do better than that you will probably lose in > availability. > > 1.5x give the same availability than 3 replicats and that for any kind > of > > erasure coding. > > FYI, Mojette transform has no constraint in terms of Galois fields. It > is the > > big advantage to use discrete geometry rather than algebra. > > > > best regards, > > bp > > > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > Loïc Dachary, Artisan Logiciel Libre > All that is necessary for the triumph of evil is that good people do > nothing. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
