From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f51.google.com ([209.85.216.51]:33403 "EHLO mail-qa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751481AbaGTOuP (ORCPT ); Sun, 20 Jul 2014 10:50:15 -0400 Received: by mail-qa0-f51.google.com with SMTP id k15so4431849qaq.10 for ; Sun, 20 Jul 2014 07:50:12 -0700 (PDT) Message-ID: <53CBD721.2080502@gmail.com> Date: Sun, 20 Jul 2014 10:50:09 -0400 From: Austin S Hemmelgarn MIME-Version: 1.0 To: Tomasz Torcz , linux-btrfs@vger.kernel.org Subject: Re: 1 week to rebuid 4x 3TB raid10 is a long time! References: <20140720140044.GB7469@mother.pipebreaker.pl> In-Reply-To: <20140720140044.GB7469@mother.pipebreaker.pl> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms020304040409050409080600" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms020304040409050409080600 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 07/20/2014 10:00 AM, Tomasz Torcz wrote: > On Sun, Jul 20, 2014 at 01:53:34PM +0000, Duncan wrote: >> TM posted on Sun, 20 Jul 2014 08:45:51 +0000 as excerpted: >> >>> One week for a raid10 rebuild 4x3TB drives is a very long time. >>> Any thoughts? >>> Can you share any statistics from your RAID10 rebuilds? >> >> >> At a week, that's nearly 5 MiB per second, which isn't great, but isn'= t=20 >> entirely out of the realm of reason either, given all the processing i= t's=20 >> doing. A day would be 33.11+, reasonable thruput for a straight copy,= =20 >> and a raid rebuild is rather more complex than a straight copy, so... >=20 > Uhm, sorry, but 5MBps is _entirely_ unreasonable. It is order-of-mag= nitude > unreasonable. And "all the processing" shouldn't even show as a blip > on modern CPUs. > This "speed" is undefendable. >=20 I wholly agree that it's undefendable, but I can tell you why it is so slow, it's not 'all the processing' (which is maybe a few hundred instructions on x86 for each block), it's because BTRFS still serializes writes to devices, instead of queuing all of them in parallel (that is, when there are four devices that need written to, it writes to each one in sequence, waiting for the previous write to finish before dispatching the next write). Personally, I would love to see this behavior improved, but I really don't have any time to work on it myself. --------------ms020304040409050409080600 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIGuDCC BrQwggScoAMCAQICAw8BRDANBgkqhkiG9w0BAQ0FADB5MRAwDgYDVQQKEwdSb290IENBMR4w HAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmlu ZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZzAeFw0xNDA1 MTIxNDEwMzJaFw0xNDExMDgxNDEwMzJaMGMxGDAWBgNVBAMTD0NBY2VydCBXb1QgVXNlcjEj MCEGCSqGSIb3DQEJARYUYWhmZXJyb2luN0BnbWFpbC5jb20xIjAgBgkqhkiG9w0BCQEWE2Fo ZW1tZWxnQG9oaW9ndC5jb20wggIiMA0GCSqGSIb3DQEBAQUAA4ICDwAwggIKAoICAQDbLUaL Gs4JTdU7sgr0MzD57CMUAv307ddC9pxooDMN3PiUvzEd5kLtBCh8KDB1wbMdfm4hte2rDd+j hM1tIq67BvNbdDPztOcBZwT2/3OVyyG4B1ddCqUyt03zGKw6Y34eHNfapsZiiItX0GBNfjHU Wv+WDo+XNha/WmGSSMv21HkftF9XA1KC9Bpr9JJI23MKK7T2g/7b3KoGZlx3ekLIJsF5B7+B DMPPDqOHQbRnccyOHEMyhM13g6WoAbU+3aKYc+C/9UsYtDV+xlvBLWagky1acstD5wOA35V6 uDRbUhD+vOjuMRMCj9jJOIYqa6AeSagBjxRnisJr0RFzQ4f+NjGCHPaFTvRvbkiXh4q22doT 0SxbNBUm7B9ANugIOtS9/VQhTWKDi//WTqZQ7Ecl4yVJbMCUg/iaRHMCGS41vqMICPszRidW rL04NwS9D2cREEY1y/xrNo0ZvKPZu6tLhxhPf7w+5rsN3+wWxGaR1hNpnVUT9AeacLKZO6W9 FsRT3Unkr91IhQATHTKYr4EAkjN/5lgvA+sxp5TxxsUnoJYrD8IHf8aYfJsAHMleBwx4xSeZ tw/n5iIjJjFZq9IRZ1zQhK62p+a5vJ2vlJHjTgavhQrfb1pUOjbqsnI4ndQ5hNosL9el4Kxq Yko+HsxVEmSwSsjq6cV2L3oz0z8NUwIDAQABo4IBWTCCAVUwDAYDVR0TAQH/BAIwADBWBglg hkgBhvhCAQ0ESRZHVG8gZ2V0IHlvdXIgb3duIGNlcnRpZmljYXRlIGZvciBGUkVFIGhlYWQg b3ZlciB0byBodHRwOi8vd3d3LkNBY2VydC5vcmcwDgYDVR0PAQH/BAQDAgOoMEAGA1UdJQQ5 MDcGCCsGAQUFBwMEBggrBgEFBQcDAgYKKwYBBAGCNwoDBAYKKwYBBAGCNwoDAwYJYIZIAYb4 QgQBMDIGCCsGAQUFBwEBBCYwJDAiBggrBgEFBQcwAYYWaHR0cDovL29jc3AuY2FjZXJ0Lm9y ZzAxBgNVHR8EKjAoMCagJKAihiBodHRwOi8vY3JsLmNhY2VydC5vcmcvcmV2b2tlLmNybDA0 BgNVHREELTArgRRhaGZlcnJvaW43QGdtYWlsLmNvbYETYWhlbW1lbGdAb2hpb2d0LmNvbTAN BgkqhkiG9w0BAQ0FAAOCAgEAIokFPcW8+cO2Clu0Ei+ehAmQRBHfV5RWJ8aMVLXOCfiJX0ch IjVSIt6I3uQaR4J1ZIAjCSPkbpfZQDaLoGFI5j8aYEQhOeKxrvOMzY9/aSUYabCJIhE/sX64 klFV0bzm+PR9cDMWeQ9BoZf0m8UROPSfDnrjEk+p04hGg3pAZMcSwCzxdb604NHjgHJmf2xG UQVzQgC6Ek/BKat0xuPTuPmtPv9OicK75CPmLZKYW3rFpCD6bhb1mm+ROcCNhniRY2LYm9YN QdlHQUzTFqj0tvuYrzNI3LNV4PjEfN8z6omPCT2Rq8/uKLseN+m8F0ioqm+cphqpmzKoDUpN nePLkqDFUFWCeWRxSjBTy4IMVUfdNXriVGihH8hyIICQiOfmmBOzhzUifdomJuTGtoXRuHVT R2f/YdrJrLnKI4f+Othdp7F3KhB4c6JiOnTEH5J8n9q3rFjt4MPRwcjIHMhmF5nZVQlgxEMo 1cPCmvG1D9tcgXbH79jjqydo9SDXhzLQob7axkzGRY96IstNcvoQ/UNsdPPfFMYlHtGz4TxT DhBjv4ERskGmKBZrfmxkXkcuTV/gcykct6Xvw9YXb8WTL4qSYHSYk9fReVLgE/L4RBUpX2JJ QvIR0AJLER165/aZlQXZtuJjnfxJtJTJZZ+Gor9h0G2kuR5Dy0JuYdBO4t4xggShMIIEnQIB ATCBgDB5MRAwDgYDVQQKEwdSb290IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5v cmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEW EnN1cHBvcnRAY2FjZXJ0Lm9yZwIDDwFEMAkGBSsOAwIaBQCgggH1MBgGCSqGSIb3DQEJAzEL BgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTE0MDcyMDE0NTAwOVowIwYJKoZIhvcNAQkE MRYEFE5tPKLxJn75oBPlTBovh9HUQMolMGwGCSqGSIb3DQEJDzFfMF0wCwYJYIZIAWUDBAEq MAsGCWCGSAFlAwQBAjAKBggqhkiG9w0DBzAOBggqhkiG9w0DAgICAIAwDQYIKoZIhvcNAwIC AUAwBwYFKw4DAgcwDQYIKoZIhvcNAwICASgwgZEGCSsGAQQBgjcQBDGBgzCBgDB5MRAwDgYD VQQKEwdSb290IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMT GUNBIENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2Fj ZXJ0Lm9yZwIDDwFEMIGTBgsqhkiG9w0BCRACCzGBg6CBgDB5MRAwDgYDVQQKEwdSb290IENB MR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2ln bmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZwIDDwFE MA0GCSqGSIb3DQEBAQUABIICAEDYf9EnPpSstv4HvWS0swr342sCM6FFusIE1ToZ82B+8ZkB TVXbH92VjB/9iH2yjJFfHVxYraYUUM67H/ZB8phHSlxYsG8qzpV+uAi0j360Gt+pTBBHQdui 3kiXL3NM0a6z52PIYmrJSxpNo1DTbU4lYDbd6+jwM7F0Y6m/hHV+YGxItOpN3vtNuCVwTRcG RlvXM/Hbpi4qdP2yEHUTGU2aH+stvtufUA9/tFtOI031isZ0YO/TEx4mU9zpwzp+DMhrjtcL YvvTODiMsNg8TjReElfrOqaeAy4GkZ5FTgMv7o9hQu5+z92dHI/avwIQsc7XC91GLIZD1DWr Mwws6rBt30fxwQG6HP26otKxGfImftFTjU1QXr8yDbf/QEq0DzA+dVlu+Sh84g8snY7XrLa/ 87GRSWb5Qr/Ytrue5cfVScdpFIxidlvHFJNgSQjgyijzF3lRmdj9oYCurYFrfHJUVy9EYIe+ DzJoZ6aeMYNbFg7+dHKXQJAxKGyfOmNLlpMgL1m50rWLUpcqHAQyjS+pejPS9WOlyB1KNOei 1UJdJblFez/aP0h7ytsWdmOT4tW6SXiWTCo7NwbucfchfxjJzUzz80KTDQqUp34Niun1iLA0 F23lTa4cb7n+ksrDTnnCvgMZwlYa8m3bZswu4cIxJLGv69jPFKXDMqtnlDhSAAAAAAAA --------------ms020304040409050409080600--