From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Bad write performance with libata-tj-stable-2.6.17.4-20060710, pcmcia based sata_sil24, PMP, and NCQ drive Date: Tue, 29 Aug 2006 22:35:14 +0900 Message-ID: <44F44292.30306@gmail.com> References: <20060828230132.GB20189@geeks.org> <44F3A8FD.6090108@gmail.com> <20060829045816.GA21746@geeks.org> <20060829075454.GA22899@geeks.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from py-out-1112.google.com ([64.233.166.182]:58352 "EHLO py-out-1112.google.com") by vger.kernel.org with ESMTP id S964969AbWH2NgJ (ORCPT ); Tue, 29 Aug 2006 09:36:09 -0400 Received: by py-out-1112.google.com with SMTP id n25so2896401pyg for ; Tue, 29 Aug 2006 06:36:08 -0700 (PDT) In-Reply-To: <20060829075454.GA22899@geeks.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Derek Taubert Cc: linux-ide@vger.kernel.org Derek Taubert wrote: > The sd cache_type is set to "write back" for this drive. I suspect that > the reads are coming from the block driver attempting to fill lines. > > # cat /sys/bus/scsi/devices/0:0:0:0/scsi_disk:0:0:0:0/cache_type > write back That's the cache inside the harddrive. To libata and SCSI, it's (almost) transparent and doesn't cause such problems. > Also, a problem here: > > # echo "none" > /sys/bus/scsi/devices/0:0:0:0/scsi_disk:0:0:0:0/cache_type > echo: write error: invalid argument > > dmesg says: > > sda: Current: sense key: Illegal Request > Additional sense: Invalid field in cdb libata doesn't support that sysfs node (yet). -- tejun