From owner-freebsd-questions@FreeBSD.ORG Sun Jun 26 08:17:15 2011 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 775171065673 for ; Sun, 26 Jun 2011 08:17:15 +0000 (UTC) (envelope-from rsimmons0@gmail.com) Received: from mail-vx0-f182.google.com (mail-vx0-f182.google.com [209.85.220.182]) by mx1.freebsd.org (Postfix) with ESMTP id 28D788FC20 for ; Sun, 26 Jun 2011 08:17:14 +0000 (UTC) Received: by vxg33 with SMTP id 33so3956909vxg.13 for ; Sun, 26 Jun 2011 01:17:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:from:reply-to:to:subject:date:user-agent :references:in-reply-to:mime-version:content-type :content-transfer-encoding:message-id; bh=W3Ba3QvLKbhBt5i3P7Usp9fNHPS+Fs5NsQKYqGp7wkc=; b=iEXNHao2tVxa4phSduepDXX7pm8A4l7YfmkVpyYSEhkPCg+e+qAYrFGn4JUnfJqne9 mGxJahMBo5e6AEicnbD+MwYqMOXe/N9LQrLftjKw3H+xj3CU9+awknRWTi0NNpOuoACI /A0oLTIZ77gNGaaxlQ0aTRv+iCECgt3tHR1gY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:reply-to:to:subject:date:user-agent:references:in-reply-to :mime-version:content-type:content-transfer-encoding:message-id; b=lQ+7QR9q9bWnq6/H/blRxMxLlk9ptzICJfvU0bAIIFP1XkKFUgrgOQ3RgBJ3AAVdMp TiUFguzN2qGvVM4cBAl9aZmBaAQSgbH7np2Uh2pnWViV1g4R04+Q/lQDF5ygX8PVukmh T7/dr3Q1/crq3YLkvzo+sdpeK5rRqtqk+vGeM= Received: by 10.52.76.74 with SMTP id i10mr6756352vdw.128.1309076233718; Sun, 26 Jun 2011 01:17:13 -0700 (PDT) Received: from skynet.localnet (pool-108-28-47-226.washdc.fios.verizon.net [108.28.47.226]) by mx.google.com with ESMTPS id o9sm2521937vbz.9.2011.06.26.01.17.12 (version=SSLv3 cipher=OTHER); Sun, 26 Jun 2011 01:17:13 -0700 (PDT) From: Robert Simmons To: freebsd-questions@freebsd.org Date: Sun, 26 Jun 2011 04:17:11 -0400 User-Agent: KMail/1.13.6 (Linux/2.6.38-8-generic; KDE/4.6.4; i686; ; ) References: <4E06180F.7090409@gmail.com> <4E06C2D1.4050601@gmail.com> <20110626074141.GB44024@dan.emsphone.com> In-Reply-To: <20110626074141.GB44024@dan.emsphone.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201106260417.11482.rsimmons0@gmail.com> Subject: Re: Performance of a USB ZIL for ZFS X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: rsimmons0@gmail.com List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 26 Jun 2011 08:17:15 -0000 On 25 Jun 2011, at 19:17, Joshua Isom wrote: > I was wondering if anyone had tried using a decent USB flash drive for > the ZIL. I know it'd be hard finding one fast enough, but some from > patriot seem like they might be suitable for home use. Part of the > idea is to just minimize hard drive thrashing and the wear and tear > associated with it. If it helps prevent the drives from going bad, > and doesn't hurt performance too bad all the better. But if it's > going to hurt performance too much or not help prevent thrashing > there isn't a point. You question is a good one, but I think the reason for your question may be off. If you want the ZIL in a separate location it is to cut down on latency rather than "thrashing". See: http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Disabling_the_ZIL_.28Don.27t.29 If your concern really really is "thrashing" please consider the cost of flash memory vs a hard drive. Replacing a bad hard drive is cheaper. After a cursory glance at newegg, you can see the price per MB for: HDD $0.09 USB flash $0.64 SSD $1.875