From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f169.google.com ([209.85.223.169]:32803 "EHLO mail-io0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756365AbbIYNqw (ORCPT ); Fri, 25 Sep 2015 09:46:52 -0400 Received: by iofh134 with SMTP id h134so110802215iof.0 for ; Fri, 25 Sep 2015 06:46:52 -0700 (PDT) Subject: Re: BTRFS as image store for KVM? To: Jim Salter , Rich Freeman References: <55F88ECC.1040604@menke.ac> <55FE0B42.50300@jrs-s.net> <56054665.1020608@gmail.com> <5605483A.7040103@jrs-s.net> Cc: Gert Menke , Btrfs BTRFS From: Austin S Hemmelgarn Message-ID: <56055019.4010506@gmail.com> Date: Fri, 25 Sep 2015 09:46:01 -0400 MIME-Version: 1.0 In-Reply-To: <5605483A.7040103@jrs-s.net> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms010006010505030202050806" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms010006010505030202050806 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-25 09:12, Jim Salter wrote: > Pretty much bog-standard, as ZFS goes. Nothing different than what's > recommended for any generic ZFS use. > > * set blocksize to match hardware blocksize - 4K drives get 4K > blocksize, 8K drives get 8K blocksize (Samsung SSDs) > * LZO compression is a win. But it's not like anything sucks without > it. No real impact on performance for most use, + or -. Just saves spa= ce. > * > 4GB allocated to the ARC. General rule of thumb: half the RAM > belongs to the host (which is mostly ARC), half belongs to the guests. > > I strongly prefer pool-of-mirrors topology, but nothing crazy happens i= f > you use striped-with-parity instead. I use to use RAIDZ1 (the rough > equivalent of RAID5) quite frequently, and there wasn't anything > amazingly sucky about it; it performed at least as well as you'd expect= > ext4 on mdraid5 to perform. > > ZFS might or might not do a better job of managing fragmentation; I > really don't know. I /strongly/ suspect the design difference between > the kernel's simple FIFO page cache and ZFS' weighted cache makes a > really, really big difference. I've been coming to that same conclusion myself over the years. I would = really love to see a drop in replacement for Linux's pagecache with=20 better performance (I don't remember for sure, but I seem to remember=20 that the native pagecache isn't straight FIFO), but the likelihood of=20 that actually getting into mainline is slim to none (can you imagine=20 though how fast XFS or ext* would be with a good caching algorithm?). > > > > On 09/25/2015 09:04 AM, Austin S Hemmelgarn wrote: >> you really need to give specifics on how you have ZFS set up in that >> case. >> > --------------ms010006010505030202050806 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 hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTI1MTM0NjAxWjBPBgkq hkiG9w0BCQQxQgRAVUEfIbyiscw1BiTDndaIC6ltfKPne6KRMjCp9gkAH5kH0o1M7h4IXdCU /+aJcWHbrj6smZ10maUah5g36W0qTzBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgBrW1nHdRFOgFCYI03Wx897bM5OBDANqpvy0dX1Y1/F+UzCB8dA uCd5gYDIpvqo4uyeQVYyWhUY2CbSJxJm+wgNON7bwa4y9QCSjsbYIi81OIFa4XKi1nfNEWfT LoRFx2NjEP3caxOUjO4YTURc7eX4ayU7wph/EEFqcdpGbCP7WW14oDHTB1/9AUKBEDwn9xsM y0JnjF1tYJpTv9u1uXrANPsf86B5nsGrRMf69ImfpCpvY8YfQ1LLpheI12YcQP5cAhYw1NGc NbbXr0STkp/vvkz1s+QXAR1Tex7nLzeMFpHnO7Skyd9yVXqdHQNDioPkaESefocnNHH3CO+a +Ei2BV1IfvP+DLJZAjbArrEsWY6KHaCfxm4etxsz4905a0+Qzs25J5EDJ8um1lFlw+R6jzb+ aIsTZq2K6+kRo6rNUBu2tEGFSsGkVKi5HoH0YFXheTp/LilZg/ojGpSnJyQggVRJDOAS/MVe quVSdlYtUHWDrZA+4X/yV2odtcTHIlCv3nrHtO4bFpGM52jA1UmvG9ZzQqV3+uaNzwsS0XsR K/EHtRC6UmpZgzf5fhhNE/Q5NWWEa47a4uUs9dbfeqLYNQIMPoW8ZIKSw9xLadhlT2TEOcfP qMtuBK2XA8oDb5bfdV/yVA1V1gql2pIFGUh3AufPbG5qNwXz/VkkfbMmZQAAAAAAAA== --------------ms010006010505030202050806--