From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Pocock Subject: very slow write to AHCI device Date: Mon, 07 May 2012 18:16:35 +0200 Message-ID: <4FA7F563.4040708@pocock.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail1.trendhosting.net ([195.8.117.5]:58652 "EHLO mail1.trendhosting.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756724Ab2EGQXH (ORCPT ); Mon, 7 May 2012 12:23:07 -0400 Received: from localhost (localhost [127.0.0.1]) by mail1.trendhosting.net (Postfix) with ESMTP id B874415870 for ; Mon, 7 May 2012 17:16:50 +0100 (BST) Received: from mail1.trendhosting.net ([127.0.0.1]) by localhost (thp003.trendhosting.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id m2iUET-iFaki for ; Mon, 7 May 2012 17:16:36 +0100 (BST) Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: linux-ide@vger.kernel.org Hi, I'm testing a problem with the following combination: - SB700/SB800 type controller in AHCI mode (in a HP Microserver N36L) - Seagate Barracuda 1TB 7k2 drive with NCQ I've got a fresh 256MB partition, formatted ext4, mounted barrier=1,data=ordered, write-cache enabled (hdparm -W 1 /dev/sdb) and shared over NFS. When the NFS client writes, - unpacking a source tarball, many small files, iostat reports speeds under 500kBytes/sec - dd conv=fsync, iostat reports about 50MB/sec If I set up a USB disk on the same box, with a partition formatted exactly the same way, the iostat reports the write speed (unpacking the same tarball) is over 5MBytes/sec - not so fast, but 10 times faster than the AHCI device. Is there anything I can do to troubleshoot this issue? Or should I just stop using this onboard SATA and go to something like an Adaptec 1405? Regards, Daniel