From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Haigh Subject: Re: Speeding up chunk size change? Date: Sun, 04 Mar 2012 13:27:44 +1100 Message-ID: <4F52D320.4080206@crc.id.au> References: <4F5272C9.3010906@crc.id.au> <4F52904E.10203@hardwarefreak.com> <4F52BDC7.5070805@crc.id.au> <4F52D259.4050907@hardwarefreak.com> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms060208040903050602050205" Return-path: In-Reply-To: <4F52D259.4050907@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: stan@hardwarefreak.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids This is a cryptographically signed message in MIME format. --------------ms060208040903050602050205 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable On 4/03/2012 1:24 PM, Stan Hoeppner wrote: > On 3/3/2012 6:56 PM, Steven Haigh wrote: >> On 4/03/2012 8:42 AM, Stan Hoeppner wrote: > [snip] >>>> blockdev --setra 8192 /dev/sd[abcdefg] >>> >>> Read-ahead is per file descriptor, and occurs at the filesystem level= =2E >>> The read-ahead value used is that of the device immediately underlyin= g >>> the filessytem. So don't bother setting these above. >> >> Interesting - I didn't think that was the case for whole disk arrays -= >> but there you go... Learnt something else :) > [snip] >>>> echo 4096> /sys/block/$i/queue/read_ahead_kb >>> Eliminate this line ^^^^ >> >> Any insight into why? I would have thought that this would help - >> however I'm not quite sure as to the values - as this is much less tha= n >> one chunk... That also being said, wouldn't it be a good idea to have >> *some* readahead? > > You read the answer up above, and commented on it. Maybe you didn't > fully understand? Or maybe it's because you don't know that these two > are functionally equivalent? > > blockdev --setra X > echo X> /sys/block/$i/queue/read_ahead_kb Ahhh - you're spot on... I didn't think they had the same functionality! --=20 Steven Haigh Email: netwiz@crc.id.au Web: http://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897 Fax: (03) 8338 0299 --------------ms060208040903050602050205 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIOSjCC BjQwggQcoAMCAQICAR4wDQYJKoZIhvcNAQEFBQAwfTELMAkGA1UEBhMCSUwxFjAUBgNVBAoT DVN0YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNp Z25pbmcxKTAnBgNVBAMTIFN0YXJ0Q29tIENlcnRpZmljYXRpb24gQXV0aG9yaXR5MB4XDTA3 MTAyNDIxMDE1NVoXDTE3MTAyNDIxMDE1NVowgYwxCzAJBgNVBAYTAklMMRYwFAYDVQQKEw1T dGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0aWZpY2F0ZSBTaWdu aW5nMTgwNgYDVQQDEy9TdGFydENvbSBDbGFzcyAxIFByaW1hcnkgSW50ZXJtZWRpYXRlIENs aWVudCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMcJg8zOLdgasSmkLhOr 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