From owner-freebsd-questions@FreeBSD.ORG Sat Feb 16 15:44:08 2013 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 9F499332 for ; Sat, 16 Feb 2013 15:44:08 +0000 (UTC) (envelope-from cpghost@cordula.ws) Received: from mail-la0-x232.google.com (la-in-x0232.1e100.net [IPv6:2a00:1450:4010:c03::232]) by mx1.freebsd.org (Postfix) with ESMTP id 2BE45F70 for ; Sat, 16 Feb 2013 15:44:07 +0000 (UTC) Received: by mail-la0-f50.google.com with SMTP id ec20so4359175lab.9 for ; Sat, 16 Feb 2013 07:44:06 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:x-received:x-originating-ip:in-reply-to:references :date:message-id:subject:from:to:cc:content-type:x-gm-message-state; bh=XJM+Gk7ATLwNRbRChOzTKHjzNekJGzmId4LlQQibIqU=; b=Se+h08JPGMnSNw8X8e9chUlXQzNYsI/aXZfbkxdW/lMH4s8b/ydpOm2Mf91fkAWXX/ N7Cj9/WV5NS3iN8k8QD1/lB63+WQxjkbn3JH3jk2yTw7JRQ+6oAewz+AmuJ/HnRQWTkf CiGQP8BELFliG+cpKjcOIrNCRVlT9Avj7F7Mepd9lPQ5YtqAilWez0do1KWUeK7bwewF pp8xdieRaaqcbquDiCo8i/NWuJ0unwzZt26CiwOmhNj95yOAnoudxKxYAA7oZTgthlB/ B08c6uuDjwOiKp5SDs3jPWEd6vxpFHHuhtg+GLBtU2HfQKhQL1fkVDUuiGp7BO2g9CGW w7WQ== MIME-Version: 1.0 X-Received: by 10.152.45.140 with SMTP id n12mr5465547lam.36.1361029446344; Sat, 16 Feb 2013 07:44:06 -0800 (PST) Received: by 10.112.45.36 with HTTP; Sat, 16 Feb 2013 07:44:06 -0800 (PST) X-Originating-IP: [93.221.168.254] In-Reply-To: <20130216144751.GC3070@schweikhardt.net> References: <20130216144751.GC3070@schweikhardt.net> Date: Sat, 16 Feb 2013 16:44:06 +0100 Message-ID: Subject: Re: Should I bother with a gvinum stripe when using a pair of SSDs? From: "C. P. Ghost" To: Jens Schweikhardt Content-Type: text/plain; charset=ISO-8859-1 X-Gm-Message-State: ALoCoQkxHJaZH4SSREODQSAF20U2bN7yTNlFJeJVTJwsVA+fULHusSqnSw6qjyxk2Ds7VwpzaYS1 Cc: questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 16 Feb 2013 15:44:08 -0000 On Sat, Feb 16, 2013 at 3:47 PM, Jens Schweikhardt wrote: > hello, world\n > > currently the only gvinum partition on my home system is a stripe for /home > across two Velociraptor HDDs. I'm thinking of replacing the HDDs with a > pair of SSDs. I was thinking of reducing complexity and in the migration > possibly no longer use gvinum at all--one less thing to configure and worry > about. > > * Would gvinum striping bring any speed advantage with a pair of SSDs? > * Or am I hitting other limits so that striping SSDs is a waste anyway? > * Should I finally take the plunge and acquaint myself with ZFS? > > System has 4GB RAM in an ASUS P5Q3 Deluxe with SATA II. It appears to me > that SATA II with 300MB/s is maxed out by a single SSD and striping it > will not improve r/w throughput. Is my simplistic reasoning correct? Jens, as always it depends on what you're trying to achieve: - max speed / lower latency? - max storage? - max redundancy? - max run-time-to-data-loss? Your choice of SSD probably means you'd like to reduce latency and maximize data throughput. Since you're going SSD, I suspect that maximizing total storage capacity is definitely not your primary concern, right? In this case, you probably won't need some space-saving RAID variants (like RAID-5, RAID-Z, ...), therefore simple striping or mirroring would be adequate. However, striping puts your data at risk: lose one SSD, and the whole volume becomes unusable. Mirroring would at least preserve some redundancy. Moreover, by NOT using ZFS, you're sacrificing the by-sector checksumming that becomes rather important with SSD whose mode of failure tends to favor single (silent!) sector corruption that may go undetected for a while and grow worse over time. You may then want a mirrored ZFS configuration if this is a concern. Each solution has its pros and cons, and there are quite some trade offs in there. > Regards, > > Jens > -- > Jens Schweikhardt http://www.schweikhardt.net/ > SIGSIG -- signature too long (core dumped) -cpghost. -- Cordula's Web. http://www.cordula.ws/