From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1P1QvD-0003SO-HA for garchives@archives.gentoo.org; Thu, 30 Sep 2010 21:44:11 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id D0063E0C6A; Thu, 30 Sep 2010 21:43:17 +0000 (UTC) Received: from mail.ukfsn.org (mail.ukfsn.org [77.75.108.10]) by pigeon.gentoo.org (Postfix) with ESMTP id 8BE4AE0C6A for ; Thu, 30 Sep 2010 21:43:17 +0000 (UTC) Received: from localhost (smtp-filter.ukfsn.org [192.168.54.205]) by mail.ukfsn.org (Postfix) with ESMTP id 9276ADEC2E for ; Thu, 30 Sep 2010 22:43:16 +0100 (BST) Received: from mail.ukfsn.org ([192.168.54.25]) by localhost (smtp-filter.ukfsn.org [192.168.54.205]) (amavisd-new, port 10024) with ESMTP id LkysipMT+R8b for ; Thu, 30 Sep 2010 22:43:16 +0100 (BST) Received: from humphrey.ukfsn.org (unknown [78.32.181.186]) by mail.ukfsn.org (Postfix) with ESMTP id 57D4BDEC22 for ; Thu, 30 Sep 2010 22:43:16 +0100 (BST) From: Peter Humphrey Organization: at home To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Normal disk speed? Date: Thu, 30 Sep 2010 22:43:14 +0100 User-Agent: KMail/1.13.5 (Linux/2.6.35-gentoo-r9; KDE/4.5.1; x86_64; ; ) References: <201009301700.17007.peter@humphrey.ukfsn.org> <4CA4BFE1.1050804@f_philipp.fastmail.net> In-Reply-To: <4CA4BFE1.1050804@f_philipp.fastmail.net> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201009302243.14819.peter@humphrey.ukfsn.org> X-Archives-Salt: 6c154721-089c-49c3-80a7-258ab1974670 X-Archives-Hash: 8d962dec583369e06980f7b1847dc1b9 On Thursday 30 September 2010 17:50:41 Florian Philipp wrote: > Am 30.09.2010 18:00, schrieb Peter Humphrey: > > On Thursday 30 September 2010 14:10:42 Florian Philipp wrote: > >> An HDD gets slower when you read the inner tracks. The angular > >> velocity is constant (5400 RPM) while the tangential velocity gets > >> lower with the radius. > > > > Are you telling us that the length of a stored bit is constant? I'd > > have thought it was the time needed to read or write a bit that > > was constant; otherwise the electronics would get extremely > > complex. In that case it's the angular velocity that counts, not > > the linear velocity, and it matters not which track your data are > > on. (If a block goes past the head twice as fast, it also occupies > > twice the space, so you're back where you were.) > > Yes, the length of a block is constant. If the innermost "ring" > (track) contains 4 blocks, the next ring contains maybe 5 blocks.[1] > > Put another way: If you could pack your bits more densely on > innermost tracks, why wouldn't you pack them that densely on the > whole disk and thereby increase the overall capacity? > > > That's the way it was with our imposing new 2MB disks in 1974, > > anyway. They occupied boxes four feet tall and six feet long, and > > had external air systems; I was one of those responsible for the > > maintenance; we were sent on a training course specifically for > > the disks. I can't remember who made them, but they were part of a > > Ferranti Argus 500 system at the then national grid control > > centre. > > > > Maybe technology has changed since then. > > Well, we are talking about devices employing the GMR effect while > also doing error correction and remapping of defect sectors > on-the-fly. I guess a little lookup table from track number to > time-per-block doesn't add too much complexity. > > You can easily test this if you have various partitions on your HDD. > Just compare dd throughput for your first partition versus your last > one. Seems like technology has moved on. Well, it has had 35 years or more. -- Rgds Peter. Linux Counter 5290, 1994-04-23.