From owner-freebsd-fs@FreeBSD.ORG Wed Jun 8 07:26:01 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B21541065672 for ; Wed, 8 Jun 2011 07:26:01 +0000 (UTC) (envelope-from numisemis@gmail.com) Received: from mail-bw0-f54.google.com (mail-bw0-f54.google.com [209.85.214.54]) by mx1.freebsd.org (Postfix) with ESMTP id 3B2AD8FC1B for ; Wed, 8 Jun 2011 07:26:00 +0000 (UTC) Received: by bwz12 with SMTP id 12so265491bwz.13 for ; Wed, 08 Jun 2011 00:26:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=ILycqe3t6IO7xKpkUOAWQvWU/oCrAECdHUxrJ47wuT8=; b=prW94cT8tvzB5yp3vF3U9tSZLRnsUU3DZUdyVpFmBythVc5ARnKum7sUOiqUQizEWL NWdOnB/NZivUZne/HW+27HcQaoiiGbuhIuvaHxyHFveg1sJgAIcpjzrnRACkz/pYsY5R ONKV5wVFf8HDu0JcYu6fO9eoo7osdjSyWnNRQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=Cs+55SDt/y/zeiR2n/UANIVL+nLTxY94k2EYudSFDcrc/CZJQJjfeBHbYdFMhoJBB3 +axecVU0Viz47A7JK9wUyDtIzxn4CeL4oZCZFEHCYPjnTrf5jKAlYhawO4bXWe+zvsuy 2a9qVXZF2zwSXwl7EXC6waBOZMjubjyzV4K+4= MIME-Version: 1.0 Received: by 10.204.152.5 with SMTP id e5mr326634bkw.138.1307517225930; Wed, 08 Jun 2011 00:13:45 -0700 (PDT) Received: by 10.204.180.139 with HTTP; Wed, 8 Jun 2011 00:13:45 -0700 (PDT) In-Reply-To: References: Date: Wed, 8 Jun 2011 09:13:45 +0200 Message-ID: From: =?UTF-8?Q?=C5=A0imun_Mikecin?= To: Robert Simmons Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-fs@freebsd.org Subject: Re: GPT and disk alignment X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 08 Jun 2011 07:26:01 -0000 2011/6/8 Robert Simmons wrote: > Ok, but can I assume that all HDDs of this type expand each of the 4K sectors so that physically they take up the same space as eight 512 > byte LBAs? AFAIK, the new 4K LBA has a smaller ECC area than the sum > of 8 ECC areas in 512 byte LBAs, so if the data area was _not_ > expanded slightly, you would never really be aligned except every x > LBAs as the shifting approaches an LBA boundary, right? Wrong, leave ECC out of the equation. ECC size is totally transparent and hidden to everything except the drive itself. Sector sizes that drives present to outside world contain only data part, so 512 or 4K is the size of data part. > For any HDDs, do I need to worry about cylinder boundaries at all? > Has the reported "disk geometry" become divorced from the physical > reality in modern disks? If I do still need to worry about cylinder > boundaries, should I basically ignore every reported geometry (BIOS, > OS) and use what is written on the sticker on the drive? > Can I just ignore the idea of "cylinder boundaries" completely when > dealing with SSDs and flash memory? Ignore geometries and cylinder boundaries for all of them (modern hard drives, SSD and flash memory). Those exist only for compatibility reasons. Physical drive geometry on modern hard drives is hidden (and probably is asymmetric), so there is no point in trying to optimize by using cylinder boundaries.