On 06/19/2013 03:14 AM, Alex Elsayed wrote: > Alex Elsayed wrote: > >> Loic Dachary wrote: >> >>> Hi Ceph, >>> >> <snip> >>> Reed-Solomon coding family is the only one that can keep the chuncks >>> unencoded and therefore concatenable. >> <snip> >> >> In my understanding, this is not strictly true - any 'systematic' code >> will have the unencoded chunks remain available in this manner, and any >> non- systematic linear code can be transformed into a systematic code with >> the same minimum distance. Fountain codes are often explicitly constructed >> to maintain this property, as in the case of RaptorQ [RFC 6330]. >> >> https://en.wikipedia.org/wiki/Systematic_code > > ...that said, Reed-Solomon is to the best of my knowledge the only space- > optimal such code. What does "space-optimal" mean ? Does it mean that Reed-Solomon will use less disk space than fountain codes to code the same number of parity chunks ? > An interesting option, however, might be to use a > fountain code over the network when distributing either replicas *or* parity > chunks, so that losses can be recovered with <1 full chunk retransmission. I would be gratefull if you could expand on this idea. I don't get it :-) Cheers > > -- > 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.
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