From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f173.google.com ([209.85.223.173]:33001 "EHLO mail-io0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753998AbbHFLSA (ORCPT ); Thu, 6 Aug 2015 07:18:00 -0400 Received: by ioii16 with SMTP id i16so77602823ioi.0 for ; Thu, 06 Aug 2015 04:17:59 -0700 (PDT) Subject: Re: Why subvolume and not just volume? To: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org References: From: Austin S Hemmelgarn Message-ID: <55C3425A.7030802@gmail.com> Date: Thu, 6 Aug 2015 07:17:46 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms070101010308080806020908" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms070101010308080806020908 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-08-06 03:23, Duncan wrote: > Martin posted on Wed, 05 Aug 2015 09:06:40 +0200 as excerpted: > >> [W]hat is the penalty of a subvolume compared to a directory? From a >> design perspective, couldn't all directories just be subvolumes? > > In addition to the performance issues mentioned by others, there's at > least one further practical reason as well. > > Snapshots stop at subvolume boundaries. It's thus quite useful to use > subvolumes to delineate the limits of the snapshot, saying, in effect, > snapshot this dir (which happens to be a subvol not just a normal dir) > recursively, but don't snapshot the subtree starting with this nested > subdir (which again is a (different) subvol). > And for some people, this is very useful functionality. I use it to=20 specifically exclude subsets of trivially reproducible data from backups = (for example, I always clone public git repositories into individual=20 subvolumes, and keep my local copy of the Portage tree on a separate one = (when it isn't on a separate filesystem that is)). --------------ms070101010308080806020908 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 hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwODA2MTExNzQ2WjBPBgkq hkiG9w0BCQQxQgRAmR+TQg4O+cPP13gkYL1KbI9iaYUANsbapIygz+e4N4QILJEmAgrqaND3 EPNhKq8G4HVIZ7q3KjBMoQZC+1vInTBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxBuVTCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTAN BgkqhkiG9w0BAQEFAASCAgBcKL8HEaB4dX8gRShqsvQF4eJw+PFMgkp1zguxPq1gXjcQUGN0 7hkDP88goRFA+tJCiUWn6XEpOR3PLKSAhGJ8MYW0vfCY569Hf9To/wkccRPsLyUYN4zBnr7q Ebs4l6Itk9BRnWa7pYXidoNynKkv0Zfxf2pYM3XUtClbn/eSA+/fE8NGUvy7oQUTaNqwobFB khkkz6UuE4QxbdxuaO3M9BvWGhXDtFEzfPpL+CMYb53s6v0DusBkMx4hjceLbyLKSAeMtnDR cRnv9o2cOfiaB7cyGscrSBvjzDP7vIh2kMbXjOzzFltbE36zpmncX38uOUIE0/URfqju+ySs p1wkq+5ga5pvQywVLtrv8rjAjWHIdu/pgMq6tzxh1LkJPPkZjn9GlqCUM58ALVhjtWQQzLfY mnmr446m5fmRv0GJjh3VcDu8BpM4c4PWlBBTeoU1N9ZYNIE771wpAQi1hL1dWvl8WRNF41hg GAPFocWp0b+syuTzHuafUUBGxg+XohNt4yuSdzHuFQyjNnh5EuwdSgCRKr7CrbliUI4Y6PKd a0SK3+AIMX0TRh5DxERtMPwtLJ4GdY7nk7vtGtMj5UJfsADVh4nfai17y2BaPtXGrsL09bDa Nk2fBTgWCV02+yn/lRETgqb7G/G2zi2MZr9Nbwv2qapCpNw4tNwV0O9OowAAAAAAAA== --------------ms070101010308080806020908--