From owner-freebsd-doc@FreeBSD.ORG Tue Jun 25 22:31:23 2013 Return-Path: Delivered-To: freebsd-doc@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id DD6D411D for ; Tue, 25 Jun 2013 22:31:23 +0000 (UTC) (envelope-from wblock@wonkity.com) Received: from wonkity.com (wonkity.com [67.158.26.137]) by mx1.freebsd.org (Postfix) with ESMTP id A13E51A4A for ; Tue, 25 Jun 2013 22:31:23 +0000 (UTC) Received: from wonkity.com (localhost [127.0.0.1]) by wonkity.com (8.14.7/8.14.7) with ESMTP id r5PMVKaD067672; Tue, 25 Jun 2013 16:31:20 -0600 (MDT) (envelope-from wblock@wonkity.com) Received: from localhost (wblock@localhost) by wonkity.com (8.14.7/8.14.7/Submit) with ESMTP id r5PMVKlh067669; Tue, 25 Jun 2013 16:31:20 -0600 (MDT) (envelope-from wblock@wonkity.com) Date: Tue, 25 Jun 2013 16:31:20 -0600 (MDT) From: Warren Block To: Frank Leonhardt Subject: Re: Handbook obsolescence scan: "The vinum Volume Manager" In-Reply-To: <51C9FF66.6020302@fjl.co.uk> Message-ID: References: <51C9CD3B.4090001@fjl.co.uk> <51C9FF66.6020302@fjl.co.uk> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (wonkity.com [127.0.0.1]); Tue, 25 Jun 2013 16:31:20 -0600 (MDT) Cc: freebsd-doc@freebsd.org X-BeenThere: freebsd-doc@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Documentation project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Jun 2013 22:31:23 -0000 On Tue, 25 Jun 2013, Frank Leonhardt wrote: > Couldn't agree more! In fact the whole disk mirroring thing still > confuses me, as there are too many options and no guide for choosing > between them. As far as I understand it, gmirror is the way to go in > most cases because you end up with two identical drives, either of > which can be salvaged from the wreckage after a crash, stuck in to > another PC and booted. ZFS is the solution if you want to spread lots > of data across lots of drives. ZFS can do mirrors, too, and almost everything else. Its weakness now is that it is relatively memory hungry. So I would advise this: gmirror(8) for data safety on machines with relatively limited memory. graid(8) for software BIOS RAID. ZFS for mirrors or more typical RAID arrays on machines with 4G of memory or more. > Actually, in practical terms, I don't see why ZFS is better than pairs > (or threes) of gmirrored drives mounted on to one file system in the > traditional way. Perhaps I just don't get it, or perhaps I'm just too > traditional to give up on the idea that it's good to know which drive > a particular file is on. It's RAID, so you get more space than mirrors, and possibly better performance for some things. ZFS RAID-Z1 (and -Z2, -Z3) have a lower vacuum coefficient than RAID-5. There are lots of nifty features, like being able to add storage without reformatting. There are other options, but I suspect the three above cover most of the needs and are what we should be suggesting to new users in the Handbook.