From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Guntsche Subject: Re: LVM performance Date: Mon, 10 Mar 2008 00:53:27 +0100 Message-ID: <3AF45EEC-EC43-4AD4-ACD1-4EEDDE798346@it-loops.com> References: <18360.8065.335494.142060@tree.ty.sabi.co.UK> <20080217074526.29d3c5c5@hardcode42.net> <20080218062604.05ae4821@szpak> <20080218154203.6e2d1483@szpak> <47BB30DF.1080006@student.tuwien.ac.at> <18364.6868.854623.613958@tree.ty.sabi.co.UK> <47BED119.4070000@student.tuwien.ac.at> <18384.63840.605334.155518@tree.ty.sabi.co.UK> <47D440D6.90509@student.tuwien.ac.at> <8D0FC34E-F0B0-4BAF-A466-2C8BC439E7FF@it-loops.com> <47D47264.4070404@student.tuwien.ac.at> Mime-Version: 1.0 (Apple Message framework v919.2) Content-Type: multipart/signed; boundary=Apple-Mail-1--833658130; micalg=sha1; protocol="application/pkcs7-signature" Return-path: In-Reply-To: <47D47264.4070404@student.tuwien.ac.at> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Apple-Mail-1--833658130 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit On Mar 10, 2008, at 0:27, Oliver Martin wrote: > > Hmm. Stripe alignment of the beginning of a file system would seem > to make sense. Otherwise, even if I tell the file system the stripe > size, how should it know where it's best to start writes? If my > stripes are 128KB, and I tell the fs, it can make an effort to write > 128KB blocks whenever possible. But if the fs starts 64KB into a > 128KB stripe, every 128KB write will cause two RMW cycles. > At least, that's how I understand it. Maybe there's something else > involved and it really doesn't make a difference? That's exactly what I ment sorry for not being clear enough. If you have a chunk size of 128KB it makes sense to align the beginning of the PV to this as well. Since the header is 64KB itself you should use a --metadatasize of 64 so it becomes 128K. I used a chunk size of 256K so I set the metadatasize to 192 (256-64). You can also use that if you want. That said, I did not see a big difference when running the benchmarks. A good way to see where the PE starts is pvs -o+pe_start Kind regards, Michael --Apple-Mail-1--833658130 Content-Disposition: attachment; filename=smime.p7s Content-Type: application/pkcs7-signature; name=smime.p7s Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIGIzCCAtww ggJFoAMCAQICEBd4Zp9b22liUjK/V/e8ZTUwDQYJKoZIhvcNAQEFBQAwYjELMAkGA1UEBhMCWkEx JTAjBgNVBAoTHFRoYXd0ZSBDb25zdWx0aW5nIChQdHkpIEx0ZC4xLDAqBgNVBAMTI1RoYXd0ZSBQ ZXJzb25hbCBGcmVlbWFpbCBJc3N1aW5nIENBMB4XDTA3MTAzMTE2MDMwMVoXDTA4MTAzMDE2MDMw MVowQzEfMB0GA1UEAxMWVGhhd3RlIEZyZWVtYWlsIE1lbWJlcjEgMB4GCSqGSIb3DQEJARYRbWlr ZUBpdC1sb29wcy5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQC/D9ePLG2ZNk/Z NXTRfUq7Rs+3k5M/nqmZ8riQYRnt8sCTj6o/fPS4qjaDf9jRfgbxViROiShFWMoBNJkKg91doJFk FYdive8ujFfKpPR6FVGu8rN/sHUZM/gowZUcqDyIMAJVr7iiWhQYxP3U4hmprJsmUaGkjBU37Bcw vJnEZ4gDCgYiZLiHUACDDfsl2xl5r6XvtXV9TsjWA3eQSeju68nQFP0PjFU+UtYfr3z1nFMJpuzE xStjCEZ+EkYBOHK+RmBaOLEfF2Rq8175oaX5ScotY61s7wjADYesS//bvdcZ11jf/R+UCE90p8iC Y1TjqqRv+zMc+VpyfG1dt9ELAgMBAAGjLjAsMBwGA1UdEQQVMBOBEW1pa2VAaXQtbG9vcHMuY29t MAwGA1UdEwEB/wQCMAAwDQYJKoZIhvcNAQEFBQADgYEAgVh3S3v4j1ydxqgc/DWXcO5RRnyfLTjU bJwYwTdaQVuykeXrT+2ITDIpOpVEqZ7xV/N9aKMM/izyQ8oMvw/J13TUm1N77kNCp5jYy1S+Ntuz bCdOdFVA5tFVn/nMfmK1Is6NjK+0GmryYPEpn8vaP9ZGy57wCpKZrwmytgm3oPQwggM/MIICqKAD AgECAgENMA0GCSqGSIb3DQEBBQUAMIHRMQswCQYDVQQGEwJaQTEVMBMGA1UECBMMV2VzdGVybiBD YXBlMRIwEAYDVQQHEwlDYXBlIFRvd24xGjAYBgNVBAoTEVRoYXd0ZSBDb25zdWx0aW5nMSgwJgYD VQQLEx9DZXJ0aWZpY2F0aW9uIFNlcnZpY2VzIERpdmlzaW9uMSQwIgYDVQQDExtUaGF3dGUgUGVy c29uYWwgRnJlZW1haWwgQ0ExKzApBgkqhkiG9w0BCQEWHHBlcnNvbmFsLWZyZWVtYWlsQHRoYXd0 ZS5jb20wHhcNMDMwNzE3MDAwMDAwWhcNMTMwNzE2MjM1OTU5WjBiMQswCQYDVQQGEwJaQTElMCMG A1UEChMcVGhhd3RlIENvbnN1bHRpbmcgKFB0eSkgTHRkLjEsMCoGA1UEAxMjVGhhd3RlIFBlcnNv bmFsIEZyZWVtYWlsIElzc3VpbmcgQ0EwgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBAMSmPFVz VftOucqZWh5owHUEcJ3f6f+jHuy9zfVb8hp2vX8MOmHyv1HOAdTlUAow1wJjWiyJFXCO3cnwK4Va qj9xVsuvPAsH5/EfkTYkKhPPK9Xzgnc9A74r/rsYPge/QIACZNenprufZdHFKlSFD0gEf6e20Txh BEAeZBlyYLf7AgMBAAGjgZQwgZEwEgYDVR0TAQH/BAgwBgEB/wIBADBDBgNVHR8EPDA6MDigNqA0 hjJodHRwOi8vY3JsLnRoYXd0ZS5jb20vVGhhd3RlUGVyc29uYWxGcmVlbWFpbENBLmNybDALBgNV HQ8EBAMCAQYwKQYDVR0RBCIwIKQeMBwxGjAYBgNVBAMTEVByaXZhdGVMYWJlbDItMTM4MA0GCSqG SIb3DQEBBQUAA4GBAEiM0VCD6gsuzA2jZqxnD3+vrL7CF6FDlpSdf0whuPg2H6otnzYvwPQcUCCT cDz9reFhYsPZOhl+hLGZGwDFGguCdJ4lUJRix9sncVcljd2pnDmOjCBPZV+V2vf3h9bGCE6u9uo0 5RAaWzVNd+NWIXiC3CEZNd4ksdMdRv9dX2VPMYIDEDCCAwwCAQEwdjBiMQswCQYDVQQGEwJaQTEl MCMGA1UEChMcVGhhd3RlIENvbnN1bHRpbmcgKFB0eSkgTHRkLjEsMCoGA1UEAxMjVGhhd3RlIFBl cnNvbmFsIEZyZWVtYWlsIElzc3VpbmcgQ0ECEBd4Zp9b22liUjK/V/e8ZTUwCQYFKw4DAhoFAKCC AW8wGAYJKoZIhvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMDgwMzA5MjM1MzI4 WjAjBgkqhkiG9w0BCQQxFgQUFDyO8Tbwtb6BoKn7xcu0ZK84UswwgYUGCSsGAQQBgjcQBDF4MHYw YjELMAkGA1UEBhMCWkExJTAjBgNVBAoTHFRoYXd0ZSBDb25zdWx0aW5nIChQdHkpIEx0ZC4xLDAq BgNVBAMTI1RoYXd0ZSBQZXJzb25hbCBGcmVlbWFpbCBJc3N1aW5nIENBAhAXeGafW9tpYlIyv1f3 vGU1MIGHBgsqhkiG9w0BCRACCzF4oHYwYjELMAkGA1UEBhMCWkExJTAjBgNVBAoTHFRoYXd0ZSBD b25zdWx0aW5nIChQdHkpIEx0ZC4xLDAqBgNVBAMTI1RoYXd0ZSBQZXJzb25hbCBGcmVlbWFpbCBJ c3N1aW5nIENBAhAXeGafW9tpYlIyv1f3vGU1MA0GCSqGSIb3DQEBAQUABIIBAJxLlEAexnoLMcXI ShE7FYMbxyn4DlzwQoEMdZxIzlHpibxsmBhWgOSD/ejCEJ0D/6SaBimwBZiQMfj3bXH5TJ064dks IWt00ZxflsaOptSkI5p0xsow088/yvj8mPTzC+P38IDMuG8kf5r0RUp2s1Z12e5vknSdeiBO03z8 JtH6HXgHgfTrG9un6jCgge/RCbf5L4kdhX7Ue1DIVyZjdBx56T5C1S2NLxrTKg6E2xt0odB4fbIV fprtO5Y+EPz7WhI4bwyaiOSJeeKfC0HmVJFbUDlBaSamTTN8xbAJbnPVXm/a/K5Odw2A6uzGQdRt tFnmd7apALY4QcNEa1YBMWsAAAAAAAA= --Apple-Mail-1--833658130--