From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f181.google.com ([209.85.223.181]:34709 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756221AbbIYOVc (ORCPT ); Fri, 25 Sep 2015 10:21:32 -0400 Received: by iofb144 with SMTP id b144so112473224iof.1 for ; Fri, 25 Sep 2015 07:21:31 -0700 (PDT) Subject: Re: BTRFS as image store for KVM? To: Timofey Titovets , Jim Salter References: <55F88ECC.1040604@menke.ac> <55FE0B42.50300@jrs-s.net> <56054665.1020608@gmail.com> <5605518B.2020103@jrs-s.net> Cc: Rich Freeman , Gert Menke , Btrfs BTRFS From: Austin S Hemmelgarn Message-ID: <56055839.9000904@gmail.com> Date: Fri, 25 Sep 2015 10:20:41 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms020600010404010208020004" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms020600010404010208020004 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-25 10:02, Timofey Titovets wrote: > 2015-09-25 16:52 GMT+03:00 Jim Salter : >> 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 blocksi= ze, 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 space. >> * > 4GB allocated to the ARC. General rule of thumb: half the RAM bel= ongs >> to the host (which is mostly ARC), half belongs to the guests. >> >> I strongly prefer pool-of-mirrors topology, but nothing crazy happens = if you >> use striped-with-parity instead. I use to use RAIDZ1 (the rough equiv= alent >> 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 re= ally >> don't know. I strongly suspect the design difference between the kern= el's >> simple FIFO page cache and ZFS' weighted cache makes a really, really = big >> difference. >> >> >> >> 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. >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs"= in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > FYI: > Linux pagecache use LRU cache algo, and in general case it's working go= od enough > I'd argue that 'general usage' should be better defined in this=20 statement. Obviously, ZFS's ARC implementation provides better=20 performance in a significant number of common use cases for Linux,=20 otherwise people wouldn't be using it to the degree they are. LRU often = gives abysmal performance for VM images in my experience, and=20 virtualization is becoming a very common use case for Linux. On top of=20 that, there are lots of applications that bypass the cache almost=20 completely, and while that is a valid option in some cases, it shouldn't = be needed most of the time. If it's just plain LRU, I may take the time at some point to try and=20 write some patches to test if SLRU works any better (as SLRU is=20 essentially ARC without the auto-tuning), although I have nowhere near=20 the resources to test something like that to the degree that would be=20 required to get it even considered for inclusion in mainline. --------------ms020600010404010208020004 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 hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTI1MTQyMDQxWjBPBgkq hkiG9w0BCQQxQgRALQwvkU6fUsq47IK9igwsrIP7Li/Lroo6vKCw50I7AoxDbBjvlrovqelZ +qlFe8q8dotMEMAxrTPiDA4TaaYYxjBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgCPvdCZ0eA7X52WzvoObLiUsa5tBLVSTNZCG8uiJrvUnc9lTB31 +8vmHeCYuDv7VRWHkT5TClWiK/5HW0bVrAPbO/0m2A3gghVd3i48YhHxtxmON1Fx7AF1VpDa ecJkErB5wlSO1ZkRxA5VugV2L6Mgp9Y4ckG936SbdWhOdoPOp3cPZuIRG8zkOLjFZ2xnnZhK UlsN5pRAVjUqkuD1ionWDlquFC6rku2vsIjr2KSK3cgAbXU6rnOLsrf1b+jLbj4c5U9KtPk0 Z72bma8Lh0r2mX4Cq8SED3c4p+ZyqWZ2f1H3eww+ENKAkOrcCoQBKHo0qVgNpKVS0ZVc+1Mo lXUSHpBYgMUDMW0smLS1Wq++WX3IRHjZgnViEgufJyuEWoxH0/3M2Z+pwECEKVNQOmPwZLS0 zT8br+NtLHA7oQH13VTeSj9nom89J5Nk+VszfaqoJuJmQ7muJndACg2uwq96MiAxmg2oombX DWkpRxex+flmFAbkqrdcfCkrpNTt9JMnxXm9aKgmQqtsgv0TYmjKv8hIJTM85gwOnECNxuGP EvUSkbfQtEst5za1wPW/UGkwjah5tom1tl0CxP3jz0f/Uy8aioGFu0+1egqBzHECmT8JsAh3 W46fwSSNX2hdpvNq/Zl9kEGVTQrLJRvBN7k80NyhJVa2ECG48YuyZFGszwAAAAAAAA== --------------ms020600010404010208020004--