From owner-freebsd-hackers Sat Jul 6 17:34: 0 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id F3EDC37B400 for ; Sat, 6 Jul 2002 17:33:56 -0700 (PDT) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7211243E09 for ; Sat, 6 Jul 2002 17:33:56 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.12.5/8.12.4) with ESMTP id g670XoLA064093; Sat, 6 Jul 2002 17:33:50 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.12.5/8.12.4/Submit) id g670XoMJ064092; Sat, 6 Jul 2002 17:33:50 -0700 (PDT) (envelope-from dillon) Date: Sat, 6 Jul 2002 17:33:50 -0700 (PDT) From: Matthew Dillon Message-Id: <200207070033.g670XoMJ064092@apollo.backplane.com> To: Bernd Walter Cc: Terry Lambert , Darren Pilgrim , ticso@cicely.de, freebsd-hackers@FreeBSD.ORG Subject: Re: How does swap work address spacewise? References: <20020705133837.GA513@HAL9000.wox.org> <20020705234126.GA12183@atrbg11.informatik.tu-muenchen.de> <3D2640A7.3EA2236B@pantherdragon.org> <20020706020656.GL48977@cicely5.cicely.de> <3D2762FE.9D9E0378@pantherdragon.org> <20020706220720.GG23704@cicely5.cicely.de> <3D277274.B5F3CE58@pantherdragon.org> <3D2776BE.A39A1110@mindspring.com> <20020706231346.GJ23704@cicely5.cicely.de> <200207062342.g66NgMri063859@apollo.backplane.com> <20020707001019.GK23704@cicely5.cicely.de> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG : :On Sat, Jul 06, 2002 at 04:42:22PM -0700, Matthew Dillon wrote: :> Negative block numbers are used by UFS to represent the indirect blocks :> associated with a file, while positive block numbers represent the :> contents of the file. : :I never saw any negative block numbers in on-disc structures. :Now I wonder if it was just hidden behind macros. :What is the reason to handle it that way? :Do you have some code reference for homework? LOGICAL block numbers, not physical block numbers. :> These are logical block numbers, which are fragment-sized (1K typically). :> So, 2^31 x 1K = 2TB. :> :> Physical block numbers are 512-byte sized, with a range of 2^32 :> in -stable. This also winds up being 2TB. So increasing the fragment :> size does not help in -stable. : :It's a proven fact that there is a 1T limit somewhere which was :explained with physical block numbers beeing signed. : :-- :B.Walter COSMO-Project http://www.cosmo-project.de test1# vnconfig -e -s labels -r reserve -S 2t vn0 test1# disklabel -r -w vn0 auto test1# disklabel vn0 ... bytes/sector: 4096 ... 8 partitions: # size offset fstype [fsize bsize bps/cpg] c: 536870912 0 unused 0 0 # (Cyl. 0 - 2097151) Theoretically VN can create up to an 8TB virtual disk because the sector size for a swap-backed VN device is 4K, but I'm not sure I would want to test the theory. With a regular file: test1# vnconfig -e -s labels -T -S 2047g vn0 test.dat test1# disklabel -r -w vn0 auto test1# disklabel vn0 ... bytes/sector: 512 ... c: 4292870144 0 unused 0 0 # (Cyl. 0 - 2 test1# ls -la test.dat -rw---xr-- 1 root wheel 2199023255552 Jul 7 00:31 test.dat test1# (of course, god help you if you tried to 'newfs' the above!) -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message