From owner-freebsd-questions@FreeBSD.ORG Tue Jul 22 19:29:45 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 8BEF26F0 for ; Tue, 22 Jul 2014 19:29:45 +0000 (UTC) Received: from be-well.ilk.org (be-well.ilk.org [23.30.133.173]) by mx1.freebsd.org (Postfix) with ESMTP id 62B582B6E for ; Tue, 22 Jul 2014 19:29:45 +0000 (UTC) Received: by be-well.ilk.org (Postfix, from userid 1147) id 1A46C33C46; Tue, 22 Jul 2014 15:22:15 -0400 (EDT) From: Lowell Gilbert To: Ralf Mardorf Subject: Re: [Bulk] Re: How much swap space for a 32 GB RAM system? References: <53CE8BB8.7030303@qeng-ho.org> <53CE8F62.8090701@tysdomain.com> <1406052132.7452.7.camel@rocketmail.com> Reply-To: freebsd-questions@freebsd.org Date: Tue, 22 Jul 2014 15:22:14 -0400 In-Reply-To: <1406052132.7452.7.camel@rocketmail.com> (Ralf Mardorf's message of "Tue, 22 Jul 2014 20:02:12 +0200") Message-ID: <44k375w655.fsf@be-well.ilk.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain Cc: freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Jul 2014 19:29:45 -0000 Ralf Mardorf writes: > On Tue, 2014-07-22 at 13:35 -0400, Michael Powell wrote: >> Since I don't use such things (me sysadmin - not a coder) I'm not as >> knowledgeable, but I seem to recall that a crash dump needs a swap >> that is as large as physical memory. > > "My 48GB swap file system isn't fully recognized. > Q. What is the max amount of swap a system can use? > A. Are you sure you want/need that much swap anyway? The old-school 2-4x > RAM doesn't really apply, though you may want a bit more than 1x > physical RAM if you are capturing a crash dump, and some systems have >>32GB RAM now. Swap can be limited by kern.maxswzone which controls the > size of metadata use to track swap (8.X default is 64MB allowing ~15GB > of swap). Note other changes are required to have >8x physical RAM for > swap." - https://commons.lbl.gov/display/~jwelcher@lbl.gov/FreeBSD > +Random+FAQ That's a little out of date, because crash dumps now default to a minidump and take much less space. You're unlikely to want a full dump and can always add a new disk for the purpose if you ever do. > Interesting thread, since there isn't an answer for Linux and I plan to > use a new FreeBSD install in the close future too. Fair enough. There's always advice to be found, but "how much swap" in a vastly less interesting or consequential question than it used to be.