From owner-freebsd-questions@FreeBSD.ORG Fri Oct 14 16:44:13 2011 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 451E6106566B for ; Fri, 14 Oct 2011 16:44:12 +0000 (UTC) (envelope-from nvass@gmx.com) Received: from mailout-eu.gmx.com (mailout-eu.gmx.com [213.165.64.43]) by mx1.freebsd.org (Postfix) with SMTP id 9427D8FC0A for ; Fri, 14 Oct 2011 16:44:11 +0000 (UTC) Received: (qmail invoked by alias); 14 Oct 2011 16:44:09 -0000 Received: from adsl-143.109.242.153.tellas.gr (EHLO [192.168.73.192]) [109.242.153.143] by mail.gmx.com (mp-eu004) with SMTP; 14 Oct 2011 18:44:09 +0200 X-Authenticated: #46156728 X-Provags-ID: V01U2FsdGVkX19BOAYxTDtB3DAM4Kh/Jx/zaGx6WL41Td2atY/rQp wFO6PJlNL3kKGc Message-ID: <4E9866CF.6010209@gmx.com> Date: Fri, 14 Oct 2011 19:43:59 +0300 From: Nikos Vassiliadis User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.17) Gecko/20110414 Thunderbird/3.1.10 MIME-Version: 1.0 To: Dennis Glatting References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Cc: freebsd-questions@freebsd.org Subject: Re: Very large swap X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 14 Oct 2011 16:44:13 -0000 On 10/14/2011 8:08 AM, Dennis Glatting wrote: > > This is kind of stupid question but at a minimum I thought it would be > interesting to know. > > What is the limitations in terms of swap devices under RELENG_8 (or 9)? > > A single swap dev appears to be limited to 32GB (there are truncation > messages on boot). I am looking at a possible need of 2-20TB (probably > more) with as much main memory that is affordable. The limit is raised to 256GB in HEAD and RELENG_8 http://svnweb.freebsd.org/base?view=revision&revision=225076 > I am working with large data sets and there are various ways of solving > the problem sets but simply letting the processors swap as they work > through a given problem is a possible technique. I would advise against this technique. Possibly, it's easier to design your program to user smaller amounts of memory and avoid swapping. After all, designing your program to use big amounts of swapped out memory *and* perform in a timely manner, can be very challenging. Nikos