From mboxrd@z Thu Jan 1 00:00:00 1970 From: Loic Dachary Subject: Re: Fwd: Reduce read latency and bandwidth for ec pool Date: Tue, 17 Mar 2015 08:48:55 +0100 Message-ID: <5507DC67.2030800@dachary.org> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="SRDUCHRRgO8thHjbh6AuAwAlH4qwOwQKH" Return-path: Received: from mail2.dachary.org ([91.121.57.175]:59325 "EHLO smtp.dmail.dachary.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751895AbbCQHs5 (ORCPT ); Tue, 17 Mar 2015 03:48:57 -0400 In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Xinze Chi Cc: Ceph Development This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --SRDUCHRRgO8thHjbh6AuAwAlH4qwOwQKH Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi, On 17/03/2015 08:27, Xinze Chi wrote: > hi, loic: >=20 > I have an idea which could reduce read latency and bandwidth for ec = pool. >=20 > But, I don't know whether it is feasible. >=20 > Such as ec pool stripe_width =3D 16384 =3D 4 * 4096, K =3D 4, M =3D= 2 >=20 > So ceph will partition the total of 16384 bytes to 4 data chunk, > and encoding 2 parity chunk >=20 > shard_0 include 0 - (4096-1) in original data; > shard_1 include 4096 - (4096*2 - 1) in original data; > shard_2 include 4096*2 - (4096 * 3 -1) in original data; > shard_3 include 4096*3 - (4096 * 4 - 1) in original data > shard_4 include parity chunk > shard_5 include parity chunk >=20 > Now if client read (offset 0, len 4096) from object, it should > read 4 shard (from 0-3) and decode all this 4 chunk. >=20 > But, this example, maybe we can compute the destination shard > based on ec pool config ,read offset and read len , we only read >=20 > shard_0 and return it to client, because shard_0 has include all data > as client need. That optimization makes sense to me. I guess you're interested in having = small objects in the pool and only read a few bytes at a time ? Cheers >=20 > Wait for your comment. >=20 > Thanks. >=20 --=20 Lo=C3=AFc Dachary, Artisan Logiciel Libre --SRDUCHRRgO8thHjbh6AuAwAlH4qwOwQKH 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) iEYEARECAAYFAlUH3GcACgkQ8dLMyEl6F203/QCdGhYhAh8c9fJD2iSpzsjvDa50 aEsAn0B7I3bhS6dR9Q6opfLnY3z7xtWs =5YlV -----END PGP SIGNATURE----- --SRDUCHRRgO8thHjbh6AuAwAlH4qwOwQKH--