From owner-freebsd-questions@FreeBSD.ORG Sat Feb 16 16:13:23 2013 Return-Path: Delivered-To: questions@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 56869214 for ; Sat, 16 Feb 2013 16:13:23 +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 F2309159 for ; Sat, 16 Feb 2013 16:13:22 +0000 (UTC) Received: from wonkity.com (localhost [127.0.0.1]) by wonkity.com (8.14.6/8.14.6) with ESMTP id r1GGDMKk087602; Sat, 16 Feb 2013 09:13:22 -0700 (MST) (envelope-from wblock@wonkity.com) Received: from localhost (wblock@localhost) by wonkity.com (8.14.6/8.14.6/Submit) with ESMTP id r1GGDMJh087599; Sat, 16 Feb 2013 09:13:22 -0700 (MST) (envelope-from wblock@wonkity.com) Date: Sat, 16 Feb 2013 09:13:22 -0700 (MST) From: Warren Block To: Jens Schweikhardt Subject: Re: Should I bother with a gvinum stripe when using a pair of SSDs? In-Reply-To: <20130216144751.GC3070@schweikhardt.net> Message-ID: References: <20130216144751.GC3070@schweikhardt.net> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (wonkity.com [127.0.0.1]); Sat, 16 Feb 2013 09:13:22 -0700 (MST) 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 16:13:23 -0000 On Sat, 16 Feb 2013, 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? That would be 300M per disk, potentially up to 600M total. It would have to be benchmarked to see if there is any real improvement. It had never occurred to me that ZFS could do RAID0, but apparently it can. Some ZFS safety features might make it a little less dangerous than RAID0 on gvinum. ZFS has some overhead and might not be as fast as gvinum. One larger SSD plus an add-in SATA III controller would be simpler. The bigger SSDs are frequently faster than the smaller ones due to internal striping layouts, so it's like getting a RAID0 setup anyway. I "slow mirror" SSDs with a backup hard drive via cron and rsync.