From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f171.google.com ([209.85.223.171]:33990 "EHLO mail-io0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756422AbbIYNF2 (ORCPT ); Fri, 25 Sep 2015 09:05:28 -0400 Received: by iofb144 with SMTP id b144so110012023iof.1 for ; Fri, 25 Sep 2015 06:05:27 -0700 (PDT) Subject: Re: BTRFS as image store for KVM? To: Rich Freeman , Jim Salter References: <55F88ECC.1040604@menke.ac> <55FE0B42.50300@jrs-s.net> Cc: Gert Menke , Btrfs BTRFS From: Austin S Hemmelgarn Message-ID: <56054665.1020608@gmail.com> Date: Fri, 25 Sep 2015 09:04:37 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms050308070406020807090306" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms050308070406020807090306 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-25 08:48, Rich Freeman wrote: > On Sat, Sep 19, 2015 at 9:26 PM, Jim Salter wrote: >> >> ZFS, by contrast, works like absolute gangbusters for KVM image storag= e. > > I'd be interested in what allows ZFS to handle KVM image storage well, > and whether this could be implemented in btrfs. I'd think that the > fragmentation issues would potentially apply to any COW filesystem, > and if ZFS has a solution for this then it would probably benefit > btrfs to implement the same solution, and not just for VM images. That may be tough to do however, the internal design of ZFS is _very_=20 different from that of BTRFS (and for that matter, every other=20 filesystem on Linux). Part of it may just be better data locality (if=20 all of the fragments of a file are close to each other, then the=20 fragmentation of the file is not as much of a performance hit), and part = of it is probably how they do caching (and I personally _do not_ want=20 BTRFS to try to do caching the way ZFS does, we have a unified pagecache = in the VFS for a reason, we should be improving that, not trying to come = up with multiple independent solutions). Even aside from that however, just saying that ZFS works great for some=20 particular use case isn't giving enough info, it has so many optional=20 features and configuration knobs, you really need to give specifics on=20 how you have ZFS set up in that case. --------------ms050308070406020807090306 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 hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTI1MTMwNDM3WjBPBgkq hkiG9w0BCQQxQgRAfBW6dcDT2ZjokPz9SPmzNcHC4MvInHk2S7tQ6RIWTFpUDzMQqLlHTP7P Hsj7wr6aCD/FwWJY+pibqB6g/OkpWjBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgB40Qg56MuuUhT6yQS+g93+VR9eN6kctZsKG21fmCxF4m9fPDxy 7xZoqjRBE/dOmiQOKloSVXbpCO0r4AXnq0Yr880YSDRrt85EhtPDi+JZEyJ6ROZ4vjjof5YS LkNyohgL1Rom3unfP+Gs7WXuT1S9gSWBteRrIFGtQGvamwetXvj9fD8gVHIhIU6gGjDUcnLq JNv4gw8wLa+Atqp7mLs+52Il+rCvLKrAzCvtQbpfuSdMKbUH+/TKLBzDqvHk+ZXWy6VxVoij e1oNzm1MRZ8cOcd/xylhK2UjONWzcfdFtRaYb18Q/M8Yo8dlV+lwoXNZwlkIA89FU25xdwHe QLE4B7LHY/WaFqoyRB/WF53ZeJ1jb7GbCT7GyXBI2hqEuejW2D6zTsYgFEnVjQVe89vsUb9R sTa25kA7Cao4Yl8zQJpeZHT4sp1GrIMpsIhRwiCP4TmmjfR7avSt+PvaboX+FnoJMjP32Ohj 4yTB+sVDWZO0puiwSTp+ZiUMpiXxIU5RaAVnc6rkFOjxkhDyUqofjB/wncI7u9t94RX54G38 NwjWtTzvSTXZJ2+TbSS4SHtK+DqZcrn2TH6xjjxyVyTAI0aWB2W6n6JJNlPyvfuo9zLfejpN Wvx4Pco9AibCVauzp8cy0nBL6D+uZnUh8H1+uFws1GxG3MApVqXiuYB0bAAAAAAAAA== --------------ms050308070406020807090306--