From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Horky Subject: Re: Striping does not increase performance. Date: Mon, 12 Mar 2012 15:34:11 +0100 Message-ID: <4F5E0963.6080708@cesnet.cz> References: <20120312125720.GL4558@voyageur.mas.nom.fr> <20120312135847.GM4558@voyageur.mas.nom.fr> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms030409010401020803090109" Return-path: In-Reply-To: <20120312135847.GM4558@voyageur.mas.nom.fr> Sender: linux-raid-owner@vger.kernel.org To: Erwan MAS Cc: Caspar Smit , linux-raid@vger.kernel.org, fio@vger.kernel.org List-Id: linux-raid.ids This is a cryptographically signed message in MIME format. --------------ms030409010401020803090109 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Hi, as for alignment, please also check md metadata format version (-e=20 switch of mdadm). The version that ensures alignment is 1.0, which=20 places the metadata information to the back of the drive. I am not an=20 expert to LVM but I would suspect that there might be similar=20 problems/options to check. I would first verify physical sector size of the drives you use. Please=20 have a look at the utility at=20 http://www.farm.particle.cz/blksztester.tar.gz. It randomly directly=20 writes e.g. 4K blocks to a block device at choosen alignment. Run it=20 with no arguments to get some help in English (README is in Czech :). If you get similar speeds for 4k-align and 4k-misalign writes, the disk=20 use 512b physical sector size. The difference should be around 300% in=20 case of 4K sectors. You may try to google for sector size according to=20 product number, but I have seen cases where official vendor websites=20 were wrong. Please note that you shold not connect the drive under test=20 through RAID controller with its own logic and/or cache, which may skew=20 the results, but rather to a stupid motherboard. I had several headaches with 4k-block drives in the past as well... Cheers Jiri Horky On 03/12/2012 02:58 PM, Erwan MAS wrote: > On Mon, Mar 12, 2012 at 02:02:36PM +0100, Caspar Smit wrote: >> Hi Erwan, >> >> I do not use partitions on the drives so the whole disk /dev/sdb is >> used as md component device, i was in the understanding that if not >> using partitions the alignment is correct or am i wrong? >> > For me it's correct . > --------------ms030409010401020803090109 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIISxDCC BGYwggNOoAMCAQICEFEmCpMc4n+cw6VfeeByroIwDQYJKoZIhvcNAQEFBQAwgZMxCzAJBgNV BAYTAlVTMQswCQYDVQQIEwJVVDEXMBUGA1UEBxMOU2FsdCBMYWtlIENpdHkxHjAcBgNVBAoT FVRoZSBVU0VSVFJVU1QgTmV0d29yazEhMB8GA1UECxMYaHR0cDovL3d3dy51c2VydHJ1c3Qu Y29tMRswGQYDVQQDExJVVE4gLSBEQVRBQ29ycCBTR0MwHhcNMDUwNjA3MDgwOTEwWhcNMTkw 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