From owner-freebsd-questions@FreeBSD.ORG Fri Jun 13 01:08:23 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 204211065673 for ; Fri, 13 Jun 2008 01:08:23 +0000 (UTC) (envelope-from dkelly@hiwaay.net) Received: from bee.hiwaay.net (bee.hiwaay.net [216.180.54.11]) by mx1.freebsd.org (Postfix) with ESMTP id D6CB48FC19 for ; Fri, 13 Jun 2008 01:08:22 +0000 (UTC) (envelope-from dkelly@hiwaay.net) Received: from [10.0.0.183] ([216.186.148.249]) (authenticated bits=0) by bee.hiwaay.net (8.13.8/8.13.8) with ESMTP id m5D0sc9g1093921 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NO); Thu, 12 Jun 2008 19:54:39 -0500 (CDT) From: David Kelly To: Kirk Strauser In-Reply-To: <200806121521.16237.kirk@strauser.com> References: <200806121521.16237.kirk@strauser.com> Message-Id: Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v924) Date: Thu, 12 Jun 2008 19:54:37 -0500 X-Mailer: Apple Mail (2.924) Cc: freebsd-questions@freebsd.org Subject: Re: Stripe sizes with gstripe X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: FreeBSD Questions List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 Jun 2008 01:08:23 -0000 On Jun 12, 2008, at 3:21 PM, Kirk Strauser wrote: > Does gstripe read an entire stripe at a time? If so, why do that > instead of > just reading a few requested blocks? If not, then is there any > advantage > to large stripes? Apparently it won't read anything larger than your stripe size which defaults to a miserable 4k. Doesn't appear the driver collects multiple pending reads and merges them into one transaction. Don't know if ATA/SATA allows that or not, believe it was called "scatter/gather" in SCSI. Built a gstripe volume a while back and played with various stripe sizes trying to maximize KB/t as shown in "systat -v" during massive file read/writes. A stripe size of 131072 (128k bytes) was the best I could get at about 43 KB/t. About 25 MB/sec each on two drives that are capable of 4x that on a Mac Pro (about 55 MB/sec single drive on inner tracks to 100 MB/sec on outer, reading with md5). Anyway, throughput was terrible with the default 4k stripe. If there is a tuning knob that I have missed, would appreciate being told what. IIRC vinum's default stripe was about 87.5kB and "systat -v" reported transactions of that size. -- David Kelly N4HHE, dkelly@HiWAAY.net ======================================================================== Whom computers would destroy, they must first drive mad.