On 20/03/2015 13:37, Andreas Joachim Peters wrote: > Hi Loic, > I looked at that some time ago. > > Table 1 in the paper says it all: > > If you care about decoding and reconstruction of data it gives a good improvement. > If you care mainly about encoding speed, it is not the optimal choice (+72.1%). > > The algorithm optimizes the reconstruction of data units. This is relevant if your read-size is typically smaller than the block-size e.g. you encode 4 MB objects and you read 4kb pages. With normal EC you get a read amplification of K*4k if a data stripe is down, while with hitchhiker you get only 2/3 of that traffic in case of (10,4). > > The most interesting to implement is probably Hitchhiker-XOR+, which you have to combine with a Vandermonde matrix, it requires that the first parity is just the xor of all data chunks. > > So, yes, there is certainly a benefit in implementing that compared to other approaches (Xorbas,LRC) since it does not involve a space overhead and opens the door to use larger K values and save space! > That sounds appealing :-) Do you think it would be more relevant to implement this as an additional Ceph plugin ? Or as a new jerasure technique ? -- Loïc Dachary, Artisan Logiciel Libre
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