From mboxrd@z Thu Jan 1 00:00:00 1970 From: Loic Dachary Subject: Locally Repairable Codes vs Pyramid Date: Mon, 02 Jun 2014 18:00:34 +0200 Message-ID: <538C9FA2.3020805@dachary.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="hTFOPgO9mDkI8aKgW9m5egxpjLOXhBWob" Return-path: Received: from smtp.dmail.dachary.org ([91.121.254.229]:58483 "EHLO smtp.dmail.dachary.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753616AbaFBQAh (ORCPT ); Mon, 2 Jun 2014 12:00:37 -0400 Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Ceph Development Cc: Dan Lambright , Xavier Hernandez This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --hTFOPgO9mDkI8aKgW9m5egxpjLOXhBWob Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Ceph, TL;DR: s/pyramid/LRC/ in the implementation of http://pad.ceph.com/p/cdsg= iant-pyramid-erasure-code for clarity Although the term "Pyramid code" has been consistently used in reference = to the technique used to reduce the network requirements when repairing f= rom the loss of a single OSD (put simply ;-), I realized today when discu= ssing with Dan Lambright and Xavier Hernandez from glusterfs that I was u= nclear about what it really means. As far as I can tell, LRC as described in http://anrg.usc.edu/~maheswaran= /Xorbas.pdf suggests an implementation that is close to what has been des= cribed during the last CDS. In contrast the pyramid code paper http://res= earch.microsoft.com/pubs/70415/tr-2007-25.pdf suggests a more sophisticat= ed approach which I do not fully understand.=20 Instead of hardcoding the word "pyramid" in the pathnames of the implemen= tation it seems better to use "LRC" instead. Cheers --=20 Lo=EFc Dachary, Artisan Logiciel Libre --hTFOPgO9mDkI8aKgW9m5egxpjLOXhBWob Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlOMn6IACgkQ8dLMyEl6F21YYQCgnaoX8skhIAf10kNmWyFP+IpG ysMAmwZRK2gSZD2UjtfynMOOj0vFppPB =w3/4 -----END PGP SIGNATURE----- --hTFOPgO9mDkI8aKgW9m5egxpjLOXhBWob--