From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f176.google.com ([209.85.223.176]:34793 "EHLO mail-io0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752031AbbIRONk (ORCPT ); Fri, 18 Sep 2015 10:13:40 -0400 Received: by iofb144 with SMTP id b144so57817614iof.1 for ; Fri, 18 Sep 2015 07:13:40 -0700 (PDT) Subject: Re: BTRFS as image store for KVM? To: Chris Murphy , Gert Menke References: <55F88ECC.1040604@menke.ac> <55FAFEB8.6030404@menke.ac> Cc: Btrfs BTRFS From: Austin S Hemmelgarn Message-ID: <55FC1C09.7030006@gmail.com> Date: Fri, 18 Sep 2015 10:13:29 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms010402000408010803000508" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms010402000408010803000508 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-17 14:35, Chris Murphy wrote: > On Thu, Sep 17, 2015 at 11:56 AM, Gert Menke wrote: >> Hi, >> >> thank you for your answers! >> >> So it seems there are several suboptimal alternatives here... >> >> MD+LVM is very close to what I want, but md has no way to cope with si= lent >> data corruption. So if I'd want to use a guest filesystem that has no >> checksums either, I'm out of luck. > > You can use Btrfs in the guest to get at least notification of SDC. If > you want recovery also then that's a bit more challenging. The way > this has been done up until ZFS and Btrfs is T10 DIF (PI). There are > already checksums on the drive, but this adds more checksums that can > be confirmed through the entire storage stack, not just internal to > the drive hardware. > > Another way is to put a conventional fs image on e.g. GlusterFS with > checksumming enabled (and at least distributed+replicated filtering). > > If you do this directly on Btrfs, maybe you can mitigate some of the > fragmentation issues with bcache or dmcache; and for persistent > snapshotting, use qcow2 to do it instead of Btrfs. You'd use Btrfs > snapshots to create a subvolume for doing backups of the images, and > then get rid of the Btrfs snapshot. > > The other option (which for some reason I almost never see anyone=20 suggest), is to expose 2 disks to the guest (ideally stored on different = filesystems), and do BTRFS raid1 on top of that. In general, this is=20 what I do (except I use LVM for the storage back-end instead of a=20 filesystem) when I have data integrity requirements in the guest. On=20 the other hand of course, most of my VM's are trivial for me to=20 recreate, so I don't often need this and just use DM-RAID via LVm. --------------ms010402000408010803000508 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 Brgwgga0MIIEnKADAgECAgMQblUwDQYJKoZIhvcNAQENBQAweTEQMA4GA1UEChMHUm9vdCBD QTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNp Z25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcwHhcN MTUwMzI1MTkzNDM4WhcNMTUwOTIxMTkzNDM4WjBjMRgwFgYDVQQDEw9DQWNlcnQgV29UIFVz 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 b20wDQYJKoZIhvcNAQENBQADggIBABr5e8W+NiTER+Q/7wiA2LxWN3UdhT3eZJjqqSlP370P KL5iWqeTfxQ67Ai/mHbJcT2PgAJ+/D2Ji+aRR03UWnU/vtOwzyDLUMstqnfl0Zs+sz/CJe7x nBA5jlpjC2DKuMVfbPze7eySaen7XSGFHKE1QoVIIpQ2kVjC4nbbJQnUbAVX1Iz29WxeVGt9 XYigz3tDPf3tglN+q23E7YjQl4abTIoM7i98yV1H9gfY8lFfKZ6jREB9+n6ie2EwS3Kat2mG tl2wBx4MfRnoSQSKsLKQ5oTwhWf0JqlFwpLfl374p0Njcykej9/jnWG8Ks1V/AXTHqI4eyIP Mf5yMZkPv7n7LS9WWKdG4Nd38iv4T2EiAaWsmgu+r81qL5CJu9AyA0SBS4ttKf6k3e63w2Mv N9R45vpQ3QhAhfWyFxFhZN95APe3YECDG3+XIRJpRYPEtHuIsOyzI70ajF93gg/BidvqKsmV MM2ccktDMfqwZXea6zey7F8Geu9R7BqjXmG2HlNuXu7e/xnHOgXf5D3wPmnRLlBhXL1Ch97a w2KjaupjpAHfFjv5kGnZXN87UvvlwzIZiKXwa3vTDwK+rrKn/sHPkfDZPSiyt/ZBIK6lX83P 34H/CzGg+Kx57rHYOIHGumIvpDa5vfWp8O0sGgawb1C2Aae4sTUVIWmIjVuGI062MYIE0TCC BM0CAQEwgYAweTEQMA4GA1UEChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNl cnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcN AQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTANBglghkgBZQMEAgMFAKCCAiEwGAYJKoZI hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTE4MTQxMzI5WjBPBgkq hkiG9w0BCQQxQgRA06sV4SGcR7spP6hJCKKkVtvLMmjf5zD6ka6722c05UIYRo+rQw4n3Z1K rpe97dcQ3SCHUPbv0P+cOPd3WarGrjBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxBuVTCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTAN BgkqhkiG9w0BAQEFAASCAgBZmU4GXcqtf34podUcqiROmhJbPMf0tzw1Nd4AYFpi97QQL2Ky fo3TYatxA/ofL3bECTh1Ne6xtpHZOnKtKxSiu1qxk/kKeyvt5rY9qwn8vjExxE1/OK91kFGD 8lKvKS7NncePmt7xgflqNVhKAxG0MHU434qF7IyRCjkq9vLuKpCUajjd5WmimV2EFuxOD4Ke oP0xBXsseqU4GIs0qQequuG0LfYgJWuc+MOFVZc6YMT14hQDBGOdEGnVkZMddmmTXOwwnKNP /UYkevP/vs4EjN7IOcRNN1a370yAE6AnaZLdFhYv3E4KlWpmCXEPdhRCxJ3ZZJtU1pqK/8FN aY4PiPt+FmlFRL4RoqHkM8xIRJGD9EQ/+motzF7v9bypozTnlGR1eefz/suPQjS66ZXjelPI uiK79GhJoG7GQlD3WEB3xQyZhqQ2Z6C5JiOr5867RhBSKA0j6XkKp9N2q2r6xa0u1LAE+7HM 6OvA2qipBCzQzkgR2676AKeyZmkBgKo1WnfLytDM2IEERii5LY+2E1LiSxFeJEeWvcs6HHcX +JPH2SDMOepybZYL2ZnVSVVrCRO9Ztpcw7BQyg89PCNLv4l1XhhbQQoM4GFq1bL9qS492P6c br7MX0NefCeDW4gqoGt1ej4uTsmaefxSiLTS0zE8DQZTzQiKJrLRSNYQEQAAAAAAAA== --------------ms010402000408010803000508--