From mboxrd@z Thu Jan 1 00:00:00 1970 From: Doug Ledford Subject: Re: Raid-10 mount at startup always has problem Date: Mon, 29 Oct 2007 11:21:56 -0400 Message-ID: <1193671316.10336.423.camel@firewall.xsintricity.com> References: <46E4A39C.8040509@amfes.com> <46E4A5F0.9090407@sauce.co.nz> <46E4A7C3.1040902@amfes.com> <471F5542.3020504@amfes.com> <471FA485.6010705@tmr.com> <47202D17.3040000@amfes.com> <1193294406.10336.76.camel@firewall.xsintricity.com> <20071026091513.GB32550@percy.comedia.it> <1193426793.10336.302.camel@firewall.xsintricity.com> <4725278E.1050306@tmr.com> <20071029074139.GA15475@percy.comedia.it> <4725DEAB.4050507@tmr.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-ufQPEbpKECxASJAyTyxu" Return-path: In-Reply-To: <4725DEAB.4050507@tmr.com> Sender: linux-raid-owner@vger.kernel.org To: Bill Davidsen Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --=-ufQPEbpKECxASJAyTyxu Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Mon, 2007-10-29 at 09:22 -0400, Bill Davidsen wrote: > > consider a storage with 64 spt, an io size of 4k and partition starting > > at sector 63. > > first io request will require two ios from the storage (1 for sector 63= , > > and one for sectors 64 to 70) > > the next 7 io (71-78,79-86,97-94,95-102,103-110,111-118,119-126) will b= e > > on the same track > > the 8th will again require to be split, and so on. > > this causes the storage to do 1 unnecessary io every 8. YMMV. > No one makes drives with fixed spt any more. Your assumptions are a=20 > decade out of date. Your missing the point, it's not about drive tracks, it's about array tracks, aka chunks. A 64k write, that should write to one and only one chunk, ends up spanning two. That increases the amount of writing the array has to do and the number of disks it busies for a typical single I/O operation. --=20 Doug Ledford GPG KeyID: CFBFF194 http://people.redhat.com/dledford Infiniband specific RPMs available at http://people.redhat.com/dledford/Infiniband --=-ufQPEbpKECxASJAyTyxu Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQBHJfqTTzP9PM7pjw8RAiJrAJwN/c96ahMziJ3CkF8Dh3D0vjxodQCePZGn UhUR26Zt1jyTtQ3qh+IgO7Q= =7Io+ -----END PGP SIGNATURE----- --=-ufQPEbpKECxASJAyTyxu--