From mboxrd@z Thu Jan 1 00:00:00 1970 From: Loic Dachary Subject: Re: Erasure code library summary Date: Wed, 19 Jun 2013 09:00:10 +0200 Message-ID: <51C156FA.2000509@dachary.org> References: <51C05123.8000002@dachary.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig1DB6DEE073692B389734DEEA" Return-path: Received: from smtp.dmail.dachary.org ([86.65.39.20]:56126 "EHLO smtp.dmail.dachary.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933853Ab3FSHAM (ORCPT ); Wed, 19 Jun 2013 03:00:12 -0400 In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Alex Elsayed Cc: ceph-devel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig1DB6DEE073692B389734DEEA Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 06/19/2013 03:14 AM, Alex Elsayed wrote: > Alex Elsayed wrote: >=20 >> Loic Dachary wrote: >> >>> Hi Ceph, >>> >> >>> Reed-Solomon coding family is the only one that can keep the chuncks >>> unencoded and therefore concatenable. >> >> >> In my understanding, this is not strictly true - any 'systematic' code= >> will have the unencoded chunks remain available in this manner, and an= y >> non- systematic linear code can be transformed into a systematic code = with >> the same minimum distance. Fountain codes are often explicitly constru= cted >> to maintain this property, as in the case of RaptorQ [RFC 6330]. >> >> https://en.wikipedia.org/wiki/Systematic_code >=20 > ...that said, Reed-Solomon is to the best of my knowledge the only spac= e- > optimal such code.=20 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 chu= nks ?=20 > An interesting option, however, might be to use a=20 > fountain code over the network when distributing either replicas *or* p= arity=20 > chunks, so that losses can be recovered with <1 full chunk retransmissi= on. I would be gratefull if you could expand on this idea. I don't get it :-)= Cheers >=20 > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" i= n > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --=20 Lo=EFc Dachary, Artisan Logiciel Libre All that is necessary for the triumph of evil is that good people do noth= ing. --------------enig1DB6DEE073692B389734DEEA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlHBVvoACgkQ8dLMyEl6F23wFgCdHA95eYWQEglr88CPjiM+alvC /CcAn3bCR1bfGuwbXE0btEQJ8iwSGjQ/ =tTtL -----END PGP SIGNATURE----- --------------enig1DB6DEE073692B389734DEEA--