From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: strange hdparm results with serverworks and pata-serverworks Date: Tue, 24 Feb 2009 08:29:30 -0500 Message-ID: <49A3F63A.2080805@rtr.ca> References: <49A30901.1@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from rtr.ca ([76.10.145.34]:41978 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752666AbZBXN3d (ORCPT ); Tue, 24 Feb 2009 08:29:33 -0500 In-Reply-To: <49A30901.1@wpkg.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tomasz Chmielewski Cc: linux-ide@vger.kernel.org Tomasz Chmielewski wrote: > I have a ProLiant BL30p G1 machine running Debian Lenny (2.6.26 kernel). > > It also has two identical, 2.5 inch WDC WD2500BEVE-00WZT0 IDE drives > (new drives, no smart/badblock errors). Both drives are connected to a > single IDE channel this machine has. > > "hdparm -t" gives me different results for these drives: ~10 MB/s for > hda, and ~20 MB/s for hdb with "serverworks" driver on Debian's 2.6.26 > kernel. > When using "pata-serverworks" with 2.6.28.7 kernel, hdparm shows the > same results (~10 MB/s for sda, ~20 MB/s for sdb). > > > However, when I run "dd if=/dev/sda of=/dev/null bs=64k", I can see with > iostat that for the first 7-8 seconds, reads are with ~10 MB/s speed. > Then, reads from sda are with ~20 MB/s or more and are on par with sdb. > > Similar dd test for sdb shows that it delivers with speed of ~20 MB/s > from the first second. > > Is there an explanation for that? .. Well, as you have shown, both hdparm and dd give the same results when doing (almost) the same test: the first 3 seconds are slow. After that, I would assume that the kernel read-ahead algorithms kick in better and improve things. But 10-20Mbytes/sec is slow for most modern drives, even for 2.5" drives. Older ones, sure, that's fine, but the newest 2.5" drives should score between 40 and 100Mbytes/sec. The drive you listed is a WD 250GB mobile drive, PATA interface. I have a very similar WD drive here (WD2500BEAS) that regularly tops 60Mbytes/sec with "hdparm -t". The difference could easily be in the chipset used to communicate with the drive. You said "serverworks" driver, and "pata-serverworks". The kernel start up logs will have more information, including the timing info chosen by libata. Cheers