From owner-freebsd-fs@FreeBSD.ORG Mon Jun 22 21:03:14 2015 Return-Path: Delivered-To: freebsd-fs@nevdull.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 59B78A1C for ; Mon, 22 Jun 2015 21:03:14 +0000 (UTC) (envelope-from quartz@sneakertech.com) Received: from douhisi.pair.com (douhisi.pair.com [209.68.5.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 3838FFC for ; Mon, 22 Jun 2015 21:03:14 +0000 (UTC) (envelope-from quartz@sneakertech.com) Received: from [10.2.2.1] (pool-173-48-121-235.bstnma.fios.verizon.net [173.48.121.235]) by douhisi.pair.com (Postfix) with ESMTPSA id 237F93F6E8; Mon, 22 Jun 2015 17:03:13 -0400 (EDT) Message-ID: <55887810.3080301@sneakertech.com> Date: Mon, 22 Jun 2015 17:03:12 -0400 From: Quartz User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 MIME-Version: 1.0 To: Xin Li CC: FreeBSD FS Subject: Re: ZFS raid write performance? References: <5587C3FF.9070407@sneakertech.com> <5587C97F.2000407@delphij.net> In-Reply-To: <5587C97F.2000407@delphij.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Jun 2015 21:03:14 -0000 >> What's sequential write performance like these days for ZFS >> raidzX? Someone suggested to me that I set up a single not-raid >> disk to act as a fast 'landing pad' for receiving files, then move >> them to the pool later in the background. Is that actually >> necessary? (Assume generic sata drives, 250mb-4gb sized files, and >> transfers are across a LAN using single unbonded GigE). > > That sounds really weird recommendation IMHO. Did "someone" explained > with the reasoning/benefit of that "landing pad"? Sort of. Something about the checksum calculations causing too much overhead. I think they were confused about sequential write vs random write, and possibly mdadm vs zfs. It was just something mentioned in passing that I didn't want to start a debate about at the time, since I wasn't 100% sure. >a single hard drive won't do much beyond 100MB/s (maybe > 120MB/s max) for sequential 128kB blocks, so that "landing pad" would > probably not very helpful assuming you can saturate your GigE network Wait, I'm confused. A single GigE has a theoretical max of like 100mb/sec. That would imply the drive is probably about the same speed?