From owner-freebsd-stable@FreeBSD.ORG Mon Feb 15 08:30:29 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3710B106566C for ; Mon, 15 Feb 2010 08:30:29 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from qmta04.emeryville.ca.mail.comcast.net (qmta04.emeryville.ca.mail.comcast.net [76.96.30.40]) by mx1.freebsd.org (Postfix) with ESMTP id 1DE9C8FC0A for ; Mon, 15 Feb 2010 08:30:28 +0000 (UTC) Received: from omta18.emeryville.ca.mail.comcast.net ([76.96.30.74]) by qmta04.emeryville.ca.mail.comcast.net with comcast id i8Te1d0011bwxycA48WVFw; Mon, 15 Feb 2010 08:30:29 +0000 Received: from koitsu.dyndns.org ([98.248.46.159]) by omta18.emeryville.ca.mail.comcast.net with comcast id i8YP1d0033S48mS8e8YQBk; Mon, 15 Feb 2010 08:32:24 +0000 Received: by icarus.home.lan (Postfix, from userid 1000) id 9CCEB1E301A; Mon, 15 Feb 2010 00:30:27 -0800 (PST) Date: Mon, 15 Feb 2010 00:30:27 -0800 From: Jeremy Chadwick To: freebsd-stable@freebsd.org Message-ID: <20100215083027.GA51038@icarus.home.lan> References: <4B786D3A.3000408@langille.org> <20100215085710.21077b9vaoqxbpgk@webmail.leidinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100215085710.21077b9vaoqxbpgk@webmail.leidinger.net> User-Agent: Mutt/1.5.20 (2009-06-14) Subject: Re: hardware for home use large storage X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 15 Feb 2010 08:30:29 -0000 On Mon, Feb 15, 2010 at 08:57:10AM +0100, Alexander Leidinger wrote: > Quoting Dan Naumov (from Mon, 15 Feb 2010 > 01:10:49 +0200): > > >Get a dock for holding 2 x 2,5" disks in a single 5,25" slot and put > >it at the top, in the only 5,25" bay of the case. Now add an > >additional PCI-E SATA controller card, like the often mentioned PCIE > >SIL3124. Now you have 2 x 2,5" disk slots and 8 x 3,5" disk slots, > >with 6 native SATA ports on the motherboard and more ports on the > >controller card. Now get 2 x 80gb Intel SSDs and put them into the > >dock. Now partition each of them in the following fashion: > > > >1: swap: 4-5gb > >2: freebsd-zfs: ~10-15gb for root filesystem > >3: freebsd-zfs: rest of the disk: dedicated L2ARC vdev > > If you already have 2 SSDs I suggest to make 4 partitions. The > additional one for the ZIL (decide yourself what you want to speed > up "more" and size the L2ARC and ZIL partitions accordingly...). > This should speed up write operations. The ZIL one should be zfs > mirrored, because the ZIL is more sensitive to disk failures than > the L2ARC: zpool add log mirror > > >GMirror your SSD swap partitions. > >Make a ZFS mirror pool out of your SSD root filesystem partitions > >Build your big ZFS pool however you like out of the mechanical > >disks you have. > >Add the 2 x ~60gb partitions as dedicated independant L2ARC devices > >for your SATA disk ZFS pool. > > BTW, the cheap way of doing something like this is to add a USB > memory stick as L2ARC: > http://www.leidinger.net/blog/2010/02/10/making-zfs-faster/ > This will not give you the speed boost of a real SSD attached via > SATA, but for the price (maybe you even got the memory stick for > free somewhere) you can not get something better. I had a feeling someone would bring up L2ARC/cache devices. This gives me the opportunity to ask something that's been on my mind for quite some time now: Aside from the capacity different (e.g. 40GB vs. 1GB), is there a benefit to using a dedicated RAM disk (e.g. md(4)) to a pool for L2ARC/cache? The ZFS documentation explicitly states that cache device content is considered volatile. Example: # zpool status storage pool: storage state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM storage ONLINE 0 0 0 mirror ONLINE 0 0 0 ad10 ONLINE 0 0 0 ad14 ONLINE 0 0 0 errors: No known data errors # mdconfig -a -t malloc -o reserve -s 256m -u 16 # zpool add storage cache md16 # zpool status storage pool: storage state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM storage ONLINE 0 0 0 mirror ONLINE 0 0 0 ad10 ONLINE 0 0 0 ad14 ONLINE 0 0 0 cache md16 ONLINE 0 0 0 And removal: # zpool remove storage md16 # mdconfig -d -u 16 # -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |