From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: SCSI vs IDE Date: Tue, 31 Aug 2004 17:28:16 +1000 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <41342890.3050501@torque.net> References: <20040831050117.80689.qmail@web53204.mail.yahoo.com> Reply-To: dougg@torque.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from borg.st.net.au ([65.23.158.22]:53676 "EHLO borg.st.net.au") by vger.kernel.org with ESMTP id S267310AbUHaH26 (ORCPT ); Tue, 31 Aug 2004 03:28:58 -0400 In-Reply-To: <20040831050117.80689.qmail@web53204.mail.yahoo.com> List-Id: linux-scsi@vger.kernel.org To: Linux Explorer Cc: linux-scsi@vger.kernel.org Linux Explorer wrote: > Hi, > > I am using SCSI disk for backup operation, and I found > out that it takes long time than IDE disk. > > Herewith I attach the two text files they give the > time taken for SCSI and IDE disks for writing 4728MB > of data using dd command. > > Can anyone tell me , why SCSI disk takes approximately > 3 times as IDE disk? > > Herewith I attach one more text file inq.txt which > gives the Inquiry information of the attached scsi > disk. > > I have tried this with adaptec and LSI logic scsi > controllers, both are taking same time. It is good to see that Digital Equipment Corporation SCSI-2 disks are still going strong. So I guess it is not a Ultra 320 or SAS disk running at 15,000 rpm. Current SCSI disks are approaching transfer speeds of 100 MB/sec while your measurement shows a write speed of 11 MB/sec. What vintage is the IDE (ATA) disk that you are using for comparison? Your measurement shows a write speed of 33 MB/sec. About the only thing that might be tweaked with your hardware is write caching. ATA disks seem to have it on all the time. For your SCSI disk, in scu try: "show pages cache-control" and look at the "Write Cache Enable" state. If it says "No" then use scu to set it to "Yes" and retest. Doug Gilbert