From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f50.google.com ([209.85.192.50]:34863 "EHLO mail-qg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757711AbbIVNVL (ORCPT ); Tue, 22 Sep 2015 09:21:11 -0400 Received: by qgt47 with SMTP id 47so115546507qgt.2 for ; Tue, 22 Sep 2015 06:21:10 -0700 (PDT) Subject: Re: RAID1 storage server won't boot with one disk missing To: Qu Wenruo , Erkki Seppala , linux-btrfs@vger.kernel.org References: <55FAD9CC.5060206@oracle.com> <56013C3C.6010005@gmail.com> <56014ECA.1050002@gmx.com> From: Austin S Hemmelgarn Message-ID: <560155C4.2080701@gmail.com> Date: Tue, 22 Sep 2015 09:21:08 -0400 MIME-Version: 1.0 In-Reply-To: <56014ECA.1050002@gmx.com> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms030602010204080905050404" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms030602010204080905050404 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-22 08:51, Qu Wenruo wrote: > > > =E5=9C=A8 2015=E5=B9=B409=E6=9C=8822=E6=97=A5 19:32, Austin S Hemmelgar= n =E5=86=99=E9=81=93: >> On 2015-09-21 16:35, Erkki Seppala wrote: >>> Gareth Pye writes: >>> >>>> People tend to be looking at BTRFS for a guarantee that data doesn't= >>>> die when hardware does. Defaults that defeat that shouldn't be used.= >>> >>> However, data is no more in danger at startup than it is at the momen= t >>> when btrfs notices a drive dropping, yet it permits IO to proceed. Is= >>> there not a contradiction? >>> >>> Personally I don't see why system startup should be a special case, i= n >>> particular as it can be very stressful situation to recover from when= >>> RAID is there just to avoid the immediate reaction when hardware brea= ks; >>> and when in practice you can do the recovery while the system is runn= ing >>> in systems where short service interruptions matter. >>> >> The difference is that we have code to detect a device not being prese= nt >> at mount, we don't have code (yet) to detect it dropping on a mounted >> filesystem. Why having proper detection for a device disappearing doe= s >> not appear to be a priority, I have no idea, but that is a separate >> issue from mount behavior. >> > > Sorry for jumping out for such a sudden, but I submitted a patchset > which is somewhat related to such degraded case. > > [PATCH 0/5] Btrfs: Per-chunk degradable check > > With that patchset, btrfs can do quite good check for degradable and > mount/remount and even mounted time. > (Return value of btrfs_check_degradable() will indicate all devices OK,= > or not all OK but degradable, or not writable degradable) > > And with that patchset, it's quite easy to add support for btrfs to > sliently switch to degraded mount option if possible. > (Along with other improvement of course) > > > For the original feedback from end user, personally I understand users > who don't want to add degraded mount option manually when a device > fails, nor don't want to add a permanent mount option info fstab, just > in case of failure. > > So personally, I'd like to add a new mount option "nodegraded", to allo= w > user to force no degraded mount. > And if neither "degraded" nor "nondegraded" is given, let btrfs to > automatically switch to degraded if possible. > > And it should also still be able to info user, either by the easily > igored dmesg, or easier to notice mount option change. > > How about this method to solve the problem? It's not a bad idea, except that it changes established usage, and there = are probably some people out there who depend on the current behavior.=20 If we do go that way, mount needs to spit out a big obnoxious warning=20 (as in, not through dmesg or mount options, but directly on stderr) if=20 the filesystem gets mounted degraded automatically. A better option=20 might be to add a compat feature bit, and if that bit is set, then use=20 the above logic, otherwise use the current logic. --------------ms030602010204080905050404 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Brgwgga0MIIEnKADAgECAgMRLfgwDQYJKoZIhvcNAQENBQAweTEQMA4GA1UEChMHUm9vdCBD QTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNp Z25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcwHhcN MTUwOTIxMTEzNTEzWhcNMTYwMzE5MTEzNTEzWjBjMRgwFgYDVQQDEw9DQWNlcnQgV29UIFVz ZXIxIzAhBgkqhkiG9w0BCQEWFGFoZmVycm9pbjdAZ21haWwuY29tMSIwIAYJKoZIhvcNAQkB FhNhaGVtbWVsZ0BvaGlvZ3QuY29tMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEA nQ/81tq0QBQi5w316VsVNfjg6kVVIMx760TuwA1MUaNQgQ3NyUl+UyFtjhpkNwwChjgAqfGd LIMTHAdObcwGfzO5uI2o1a8MHVQna8FRsU3QGouysIOGQlX8jFYXMKPEdnlt0GoQcd+BtESr pivbGWUEkPs1CwM6WOrs+09bAJP3qzKIr0VxervFrzrC5Dg9Rf18r9WXHElBuWHg4GYHNJ2V Ab8iKc10h44FnqxZK8RDN8ts/xX93i9bIBmHnFfyNRfiOUtNVeynJbf6kVtdHP+CRBkXCNRZ qyQT7gbTGD24P92PS2UTmDfplSBcWcTn65o3xWfesbf02jF6PL3BCrVnDRI4RgYxG3zFBJuG qvMoEODLhHKSXPAyQhwZINigZNdw5G1NqjXqUw+lIqdQvoPijK9J3eijiakh9u2bjWOMaleI SMRR6XsdM2O5qun1dqOrCgRkM0XSNtBQ2JjY7CycIx+qifJWsRaYWZz0aQU4ZrtAI7gVhO9h pyNaAGjvm7PdjEBiXq57e4QcgpwzvNlv8pG1c/hnt0msfDWNJtl3b6elhQ2Pz4w/QnWifZ8E BrFEmjeeJa2dqjE3giPVWrsH+lOvQQONsYJOuVb8b0zao4vrWeGmW2q2e3pdv0Axzm/60cJQ haZUv8+JdX9ZzqxOm5w5eUQSclt84u+D+hsCAwEAAaOCAVkwggFVMAwGA1UdEwEB/wQCMAAw VgYJYIZIAYb4QgENBEkWR1RvIGdldCB5b3VyIG93biBjZXJ0aWZpY2F0ZSBmb3IgRlJFRSBo ZWFkIG92ZXIgdG8gaHR0cDovL3d3dy5DQWNlcnQub3JnMA4GA1UdDwEB/wQEAwIDqDBABgNV HSUEOTA3BggrBgEFBQcDBAYIKwYBBQUHAwIGCisGAQQBgjcKAwQGCisGAQQBgjcKAwMGCWCG SAGG+EIEATAyBggrBgEFBQcBAQQmMCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3NwLmNhY2Vy dC5vcmcwMQYDVR0fBCowKDAmoCSgIoYgaHR0cDovL2NybC5jYWNlcnQub3JnL3Jldm9rZS5j cmwwNAYDVR0RBC0wK4EUYWhmZXJyb2luN0BnbWFpbC5jb22BE2FoZW1tZWxnQG9oaW9ndC5j b20wDQYJKoZIhvcNAQENBQADggIBADMnxtSLiIunh/TQcjnRdf63yf2D8jMtYUm4yDoCF++J jCXbPQBGrpCEHztlNSGIkF3PH7ohKZvlqF4XePWxpY9dkr/pNyCF1PRkwxUURqvuHXbu8Lwn 8D3U2HeOEU3KmrfEo65DcbanJCMTTW7+mU9lZICPP7ZA9/zB+L0Gm1UNFZ6AU50N/86vjQfY WgkCd6dZD4rQ5y8L+d/lRbJW7ZGEQw1bSFVTRpkxxDTOwXH4/GpQfnfqTAtQuJ1CsKT12e+H NSD/RUWGTr289dA3P4nunBlz7qfvKamxPymHeBEUcuICKkL9/OZrnuYnGROFwcdvfjGE5iLB kjp/ttrY4aaVW5EsLASNgiRmA6mbgEAMlw3RwVx0sVelbiIAJg9Twzk4Ct6U9uBKiJ8S0sS2 8RCSyTmCRhJs0vvva5W9QUFGmp5kyFQEoSfBRJlbZfGX2ehI2Hi3U2/PMUm2ONuQG1E+a0AP u7I0NJc/Xil7rqR0gdbfkbWp0a+8dAvaM6J00aIcNo+HkcQkUgtfrw+C2Oyl3q8IjivGXZqT 5UdGUb2KujLjqjG91Dun3/RJ/qgQlotH7WkVBs7YJVTCxfkdN36rToPcnMYOI30FWa0Q06gn F6gUv9/mo6riv3A5bem/BdbgaJoPnWQD9D8wSyci9G4LKC+HQAMdLmGoeZfpJzKHMYIE0TCC BM0CAQEwgYAweTEQMA4GA1UEChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNl cnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcN AQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DANBglghkgBZQMEAgMFAKCCAiEwGAYJKoZI hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTIyMTMyMTA4WjBPBgkq hkiG9w0BCQQxQgRAQbxzuPcDDAUE5/37a3VzXZ2u5YYbD/pcYn6WpDP++QiPusL8CKCZSfSb JcX/10tMvnPE/fK9E8p2yec6bmgmnzBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgB+PuNUIFKW4b2jQbfExwYWSXW5pxB4BnZW2yLlVf6SNyAkvKfa A6nEuzqlD5OVZjJuvpI0eF6sWrs2JW18vLVGAb9+cx1CoBiKOHl1IH0WzM1b8Mb0p9PcCCxv Knx6AnPHiNdWjfV6GqKEwZnwJwoTNHYlVFH852OXX43YNi72MtCI1rFf7LfApZr2Ddolm6Ap tAc0WewKJTqi22K0AuGVkh3Vi372uZlBDxZ+OcgBtmmLENxNzZtwRT0JVfH7wvuxPrIfa3ML hTMIWPH11fLfgvYRgb8h2pQlvrysOTaUcAmGikkJt9mX0oaPT+yXGN0PWx59cVj6XUb7LKwp EW7HdsZsvUIlQRIfoWkmUGJ9rtOIzQQoJ0Kh7ZR0GpckDrOlJdZROx89CalVUmAAIC6Tga06 0JwK4sAgYMH125iJ+n/M8iDc7I8H4MQ+8f9D7mwx2J+LT0AlxH8O7bztJ10UVNTEgLx0nwBa J9Gt+Z5AmHrFaA+OPJIul2ggmY9sJSykX8MxLDqZvcLv5vCTZ+Dc97IcRF+Ctzqa5o1zB+gH XPiqt4GLImTmgP5wmTZ79WmKjfuDiqzItXby7q3EXICW2S0vtu8KopWfL4SYbTxASiYJvRc6 FcbC1FBBL5EZgqwM3eYF6byRTRRtEO5A1vpbT0PRZQaqQUXaL/ULlvA2kgAAAAAAAA== --------------ms030602010204080905050404--