From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [Bug 10846] New: Slow write on LSISAS1068E (SAS6/iR) on kernel >= 2.6.22 Date: Mon, 02 Jun 2008 10:11:03 -0500 Message-ID: <1212419463.3369.10.camel@localhost.localdomain> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from accolon.hansenpartnership.com ([76.243.235.52]:33680 "EHLO accolon.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751244AbYFBPLI (ORCPT ); Mon, 2 Jun 2008 11:11:08 -0400 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: bugme-daemon@bugzilla.kernel.org Cc: linux-scsi@vger.kernel.org On Mon, 2008-06-02 at 07:57 -0700, bugme-daemon@bugzilla.kernel.org wrote: > Very easy: We also check for an untar of the kernel (5x slower) > debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count= =3D60000 > 60000+0 enregistrements lus > 60000+0 enregistrements =C3=A9crits > 614400000 octets (614 MB) copi=C3=A9s, 1,17602 seconde, 522 MB/s > debian-test:~# uname -a > Linux debian-test.pr.univmed.fr 2.6.19.7 #1 SMP Fri May 30 15:55:50 > CEST 2008 > i686 GNU/Linux >=20 > debian:~# dd if=3D/dev/zero of=3Dtest.cdrom bs=3D10k count=3D60000 > 60000+0 records in > 60000+0 records out > 614400000 bytes (614 MB) copied, 7.51225 seconds, 81.8 MB/s > debian:~# uname -a > Linux debian 2.6.22-4-vserver-686 #1 SMP Tue Feb 12 22:02:04 UTC 2008 > i686 > GNU/Linux What exactly is test.cdrom on? A single disk? If so, then your first result is definitely bogus. The maximum bandwidth of a single SAS link is 300 MB/s, so it looks like the kernel is either caching the write or has timing issues. For a direct to platter speed, the data sheet for your drive gives 55-89MB/s, so I'd say 81.8 is well within the range. James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html