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 1RKoL2-0005Eb-1F for garchives@archives.gentoo.org; Mon, 31 Oct 2011 09:39:28 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 4E615E0345; Mon, 31 Oct 2011 09:39:14 +0000 (UTC) Received: from mail-gy0-f181.google.com (mail-gy0-f181.google.com [209.85.160.181]) by pigeon.gentoo.org (Postfix) with ESMTP id BFB6121C021 for ; Mon, 31 Oct 2011 09:38:23 +0000 (UTC) Received: by gye5 with SMTP id 5so7806059gye.40 for ; Mon, 31 Oct 2011 02:38:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=Rp0mt0BWx+havVgTHO8gJyAblOfX5vU/ZNFrAiqhGiw=; b=A4sVoGsJdJeBJlL95UzM80iaXpkuXhkUwFC5MGmlJbR3JVHuld7Cy6v2LOMXh3rZpF tSU7yXhu3+hsEPLurBzgAFfZu6rYA6OMMzOBc6j1e0akLKLB6j5nm2W9So6ep7wi0BkL M7P2VPpOKJHveyYB7NOusaKO1NI8dIrPkAZ4g= Received: by 10.42.158.3 with SMTP id f3mr21732963icx.7.1320053903043; Mon, 31 Oct 2011 02:38:23 -0700 (PDT) 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 Received: by 10.42.179.7 with HTTP; Mon, 31 Oct 2011 02:38:02 -0700 (PDT) In-Reply-To: References: <4EA9A5F7.9050904@gmail.com> From: James Broadhead Date: Mon, 31 Oct 2011 09:38:02 +0000 Message-ID: Subject: Re: [gentoo-user] the same hard-drives, different number of sectors... To: gentoo-user@lists.gentoo.org Content-Type: text/plain; charset=UTF-8 X-Archives-Salt: 9fb15837-3837-420f-8acd-1758dd382099 X-Archives-Hash: 1c4b9a87a015f796639e84e9bbff0eb5 On 27 October 2011 20:35, Mark Knecht wrote: > On Thu, Oct 27, 2011 at 11:41 AM, Jarry wrote: >> Hi, perhaps someone could explain this to me: >> >> I have bouth two the same hard-drives. The same model >> (Hitachi HUA722050CLA330), the same firmware (JP20A3EA), >> the same size (500GB). Well, not exactly. Both hdparm >> and fdisk report different number of sectors (976771055 >> versus 976773168). Although not a big difference, yet >> I expected them to be exactly the same (want to use >> them for raid1). >> >> So how is it possible they do not have the same number >> of sectors? I have bought them from one supplier, even >> their serial numbers are very close (only the last 2 >> characters out of 24 are different)... >> >> Jarry > > Maybe one has some stuff mapped out due to bad blocks found during > manufacturing or something like that? Not sure what it will tell you > but have you run smartctl on the drives and looked around at what they > tell you to find any differences? > > - Mark During normal operation, if a bad block is detected, that sector is marked as 'bad', and a one of the free sectors (which are additional to your totals) is allocated to replace it. This is called Re-Allocating Sectors, and according to the Google paper[1], which seems to be the only authoritative (non-marketing, non industry-funded) source on hard-drive failure, re-allocated sectors are indicative of impending drive failure. You can check your Re-Allocated sector count using smartmontools (but I recommend that you try gsmartcontrol in sunrise, which makes life easier). This is made more complicated by the fact that if bad sectors (below a manufacturing threshold) are detected in factory testing, they will re-allocate them, and reset the SMART counter to Zero (the drive _is_ brand new after all!). Thus, you can buy two of the exact same model of drive, and yet have different numbers of available sectors. It is also possible that something entirely different is at play. [1] labs.google.com/papers/disk_failures.pdf