From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw-02.dd24.net ([193.46.215.43]:33753 "EHLO mailgw-02.dd24.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751026AbcFDRhZ (ORCPT ); Sat, 4 Jun 2016 13:37:25 -0400 Message-ID: <1465061839.6689.9.camel@scientia.net> Subject: Re: btrfs From: Christoph Anton Mitterer To: Chris Murphy Cc: Austin S Hemmelgarn , Btrfs BTRFS Date: Sat, 04 Jun 2016 19:37:19 +0200 In-Reply-To: References: <1464819934.6742.71.camel@scientia.net> <1464975482.6679.11.camel@scientia.net> <6f18c0d1-8ac5-c325-0ba8-ffb949c54554@gmail.com> <1465005092.6648.39.camel@scientia.net> <57528238.6080809@gmail.com> Content-Type: multipart/signed; micalg="sha-512"; protocol="application/x-pkcs7-signature"; boundary="=-qHhaF2KhldQ0eIItycjl" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: --=-qHhaF2KhldQ0eIItycjl Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sat, 2016-06-04 at 11:00 -0600, Chris Murphy wrote: > SNIA's DDF 2.0 spec Rev 19 > page 18/19 shows 'RAID-1 Simple Mirroring" vs "RAID-1 Multi- > Mirroring" And DDF came how many years after the original RAID paper and everyone understood RAID1 as it was defined there?=C2=A01987 vs. ~2003 or so? Also SINA's "standard definition" seems pretty strange, doesn't it? They have two RAID1, as you say: - "simple mirroring" with n=3D2 - "multi mirrioring" with n=3D3 I wouldn't see why the n=3D2 case is "simpler" than the n=3D3 case, neither why the n=3D3 case is multi and the n=3D2 is not (it's also already multiple disks). Also why did they allow n=3D3 but not n>=3D3? If n=3D4 wouldn't make sense, why would n=3D3, compared to n=3D2? Anyway,... - the original paper defines it as n mirrored disks - Wikipedia handles it like that - the already existing major RAID implementation (MD) in the Linux =C2=A0 kernel handles it like that - LVM's native mirroring, allows to set the number of mirrors, i.e. it =C2=A0 allows for everything >=3D2 which is IMHO closer to the common meani= ng =C2=A0 of RAID1 than to btrfs' two-duplicates So even if there would be some reasonable competing definition (and I don't think the rather proprietary DDF is very reasonable here), why using one that is incomptabible with everything we have in Linux? Cheers, Chris. --=-qHhaF2KhldQ0eIItycjl Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCCEmow ggXiMIIDyqADAgECAhBctkhuRwyYxn/2gNtkSuKNMA0GCSqGSIb3DQEBCwUAMH0xCzAJBgNVBAYT AklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0 aWZpY2F0ZSBTaWduaW5nMSkwJwYDVQQDEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTAeFw0xNTEyMTYwMTAwMDVaFw0zMDEyMTYwMTAwMDVaMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQK Ew1TdGFydENvbSBMdGQuMSkwJwYDVQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTEjMCEGA1UEAxMaU3RhcnRDb20gQ2xhc3MgMiBDbGllbnQgQ0EwggEiMA0GCSqGSIb3DQEBAQUA A4IBDwAwggEKAoIBAQDuD1CMlQkjhKz1UGqP1jeiTiH9MgllRz6vOPrVG/eE0H/J4QQLV/PeL8RT 4xc44bEzsoJu0IhwnEchb+TxE/qw88w7hxODuw3N8Faxix6a1jp83+RWvZHZf78+O+3GYBpekZfT Oe9A/FoTXbcgwZfLTMQodn+ckNnX31M/1M2f2/7VA7QBlvihontyHQOlIlryQXnGI0UMCD21oopK 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