From owner-freebsd-hackers@FreeBSD.ORG Sat Oct 11 18:10:34 2008 Return-Path: Delivered-To: freebsd-hackers@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A4732106568E; Sat, 11 Oct 2008 18:10:34 +0000 (UTC) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.freebsd.org (Postfix) with ESMTP id 7DC9A8FC18; Sat, 11 Oct 2008 18:10:34 +0000 (UTC) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.14.1/8.14.1) with ESMTP id m9BIAHff059978; Sat, 11 Oct 2008 11:10:17 -0700 (PDT) Received: (from dillon@localhost) by apollo.backplane.com (8.14.1/8.13.4/Submit) id m9BIAGPw059975; Sat, 11 Oct 2008 11:10:16 -0700 (PDT) Date: Sat, 11 Oct 2008 11:10:16 -0700 (PDT) From: Matthew Dillon Message-Id: <200810111810.m9BIAGPw059975@apollo.backplane.com> To: Danny Braniss References: Cc: freebsd-hackers@FreeBSD.org, Jeremy Chadwick , Mike Meyer Subject: Re: ZFS boot X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 11 Oct 2008 18:10:34 -0000 :To Matt: : since 'small' nowadays is big enough to hold /, what advantages are there :in having root split up? :also, having this split personality, what if the disk goes? the hammer/zfs :is probably raided ... You mean /boot + root , or do you mean /root vs /usr vs /home? I'll answer both. With regards to /boot + root. A small separate /boot partition (256m) allows your root filesystem to use an arbitrarily complex topology. e.g. multiple geom layers, weird zfs setups, etc. So you get flexibility that you would otherwise not have if you went with a directly-bootable ZFS root. /boot can be as complex as boot2 allows. There's nothing preventing it from being RAIDed if boot2 supported that, and there's nothing preventing it (once you had ZFS boot capabilities) from being ZFS using a topology supported by boot2. Having a sparate /boot allows your filesystem root to use topologues boot2 would otherwise not support. With regards to the traditional BSD partitioning scheme, having a separate /usr, /home, /tmp, etc... there's no reason to do that stuff any more with ZFS (or HAMMER). You just need one, and can break it down into separate management domains within the filesystem (e.g. HAMMER PFS's). That's a generic statement of course, there will always be situations where you might want to partition things out separately. Most linux dists don't bother with multiple partitions any more. They just have '/' and maybe a small boot partition, and that's it. -Matt Matthew Dillon