From owner-freebsd-fs@freebsd.org Sat Aug 1 00:37:20 2015 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 10C439B0C7A for ; Sat, 1 Aug 2015 00:37:20 +0000 (UTC) (envelope-from quartz@sneakertech.com) Received: from douhisi.pair.com (douhisi.pair.com [209.68.5.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E918F14A5 for ; Sat, 1 Aug 2015 00:37:19 +0000 (UTC) (envelope-from quartz@sneakertech.com) Received: from [10.2.2.1] (pool-173-48-121-235.bstnma.fios.verizon.net [173.48.121.235]) by douhisi.pair.com (Postfix) with ESMTPSA id 1108D3F71D for ; Fri, 31 Jul 2015 20:37:12 -0400 (EDT) Message-ID: <55BC14B7.9010009@sneakertech.com> Date: Fri, 31 Jul 2015 20:37:11 -0400 From: Quartz MIME-Version: 1.0 To: FreeBSD FS Subject: ZFS: Disabling ARC? Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 01 Aug 2015 00:37:20 -0000 Can someone help clear up a few ZFS basics for me? A few recent threads about ARC issues and memory-induced panics have made me realize I'm not 100% sure I understand ARC as well as I thought I did. Say you have a ZFS file server that houses very large single files which are very infrequently accessed. For the sake of argument, let's say you're using ZFS on a home server for your family, and it holds exclusively a whole bunch of multi-gig bluray rips or whatever (nothing else). When someone wants to watch something, they copy the file to their desktop and watch it there. Although the family will watch several videos each day, any given file will only be accessed maybe once every couple months. (I know streaming would make more sense in real life, and that this example is kinda silly in general, but ignore that for now). If I understand ARC correctly this would be a worst case scenario, right? Besides hogging ram, would ARC cause any problems here? Would disabling ARC and devoting the ram to other things be a wise idea? Is disabling ARC ever a wise idea?