From owner-freebsd-questions@FreeBSD.ORG Wed Feb 19 03:58:49 2014 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id EAE49ACA for ; Wed, 19 Feb 2014 03:58:48 +0000 (UTC) Received: from h3lix.wtfayla.net (helix.wtfayla.net [24.105.170.68]) (using TLSv1 with cipher ADH-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id A254012D7 for ; Wed, 19 Feb 2014 03:58:48 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by h3lix.wtfayla.net (Postfix) with ESMTP id 0442884AEE for ; Tue, 18 Feb 2014 22:58:02 -0500 (EST) Received: from h3lix.wtfayla.net ([127.0.0.1]) by localhost (h3lix.wtfayla.net [127.0.0.1]) (maiad, port 10024) with ESMTP id 33273-07 for ; Tue, 18 Feb 2014 22:58:01 -0500 (EST) Received: from helix.wtfayla.net (helix.wtfayla.net [24.105.170.68]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by h3lix.wtfayla.net (Postfix) with ESMTPS id A635384AD3 for ; Tue, 18 Feb 2014 22:58:01 -0500 (EST) Date: Tue, 18 Feb 2014 22:58:01 -0500 (EST) From: freebsd@fongaboo.com X-X-Sender: fongaboo@helix.wtfayla.net To: questions@freebsd.org Subject: Re: ZFS on Hardware RAID controller In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Feb 2014 03:58:49 -0000 I was speaking to someone else about this today, and it eventually became apparent that we were getting into a sort-of Abbott-and-Costello-Who's-on-First confusion... because apparently people can mean different things when they use the term 'JBOD'. What I have always meant when I say 'JBOD' is a (not really) RAID mode that simply concatenates the drives into one volume in a serial fashion, ie. 'spanning'. Most RAID controllers and RAID-enabled NAS units that I have interacted with in my life have offered this mode and referred to it as 'JBOD'. In this kind of mode, the motherboard and the OS still thinks it sees only a single volume. So now I am gathering that this is also not ideal for ZFS, since it would still not be aware of multiple physical volumes and be unable to optimize accordingly. I'm learning for the first time that sometimes 'JBOD' can also refer to each individual drive being mounted separately at least as far as the controller and the motherboard is concerned. I just want to confirm 100% that this is how you are recommending multiple drives be configured for ZFS. Because when I started the thread I was thinking of JBOD as 'spanning'. FONG On Tue, 18 Feb 2014, Eitan Adler wrote: > On Tue, Feb 18, 2014 at 5:27 PM, wrote: >> >> When we spoke, you noted that when installing ZFS on multiple disks >> connected to a hardware RAID controller, it is best to config it to JBOD. > > There are a few reasons for this. > (a) Hardware RAID serves as a single point of failure: if the > contoller dies you have neither disk > (b) As Andrew noted , using hardware RAID means that ZFS won't be able > to tell which disk is which. The ZFS management tools won't work as > expected (they will show only one disk). > (c) Since ZFS implements RAID itself it can use knowledge about the > physical disks for better performance > > Also see: https://en.wikipedia.org/wiki/ZFS#ZFS_and_hardware_RAID > >> I tried to explain this to a colleague, but they were skeptical. Would you >> (or anyone) be willing to give me a one or two line sales-pitch on > > "ZFS does RAID better than the controller." > >> why one >> should abandon traditional notions of RAID performance in favor of allowing >> ZFS to do disk management? > > The goal isn't to give up on RAID but move its implementation to ZFS. > > -- > Eitan Adler > Source, Ports, Doc committer > Bugmeister, Ports Security teams > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >