From owner-freebsd-stable@FreeBSD.ORG Sun Jan 24 18:40:37 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 4ADBF106566C; Sun, 24 Jan 2010 18:40:37 +0000 (UTC) (envelope-from dan.naumov@gmail.com) Received: from mail-yw0-f197.google.com (mail-yw0-f197.google.com [209.85.211.197]) by mx1.freebsd.org (Postfix) with ESMTP id CFA748FC18; Sun, 24 Jan 2010 18:40:36 +0000 (UTC) Received: by ywh35 with SMTP id 35so2199414ywh.7 for ; Sun, 24 Jan 2010 10:40:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type :content-transfer-encoding; bh=cYTS0m2zo4yDD/C80NV/kKNkjUleB0nYq6cDz3m1o8M=; b=E/QHnw9cxELemG6LgKrCQFM00BIeOJXlPkCLLH7bNWlgqbmNLl95XVNSie0qyuFBGt ak510/HzecvrOJg+q7TJpoobuntrIl0o0A+HM+9FIcNC+yrA2AtxSFyfSnUTiatyN2xw QW06WJsoILZcAjyLjPI27iCMpw8JpBftAOuRI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=McVl6IfCbStweIGUId0p5GYs2NDRQnZfA1tzwHQ4QcA5KKsoBb4f9oKiWRc3HdXftV 9VRwxZO786iWEOOvqUU3lht82fN4Yts15TFkg4Ghcsm5dfCcGkdhor15ubMc/JrB2HL1 8s/vXLjqqAvey+UrP2bOMluaxJ6sKYt9MUQMw= MIME-Version: 1.0 Received: by 10.101.133.37 with SMTP id k37mr6619685ann.237.1264358436052; Sun, 24 Jan 2010 10:40:36 -0800 (PST) In-Reply-To: <883b2dc51001241034u40c97fdet83eb1e6edb5f4df4@mail.gmail.com> References: <883b2dc51001240905r4cfbf830i3b9b400969ac261b@mail.gmail.com> <883b2dc51001241034u40c97fdet83eb1e6edb5f4df4@mail.gmail.com> Date: Sun, 24 Jan 2010 20:40:36 +0200 Message-ID: From: Dan Naumov To: Jason Edwards , FreeBSD-STABLE Mailing List , freebsd-questions@freebsd.org, freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: Subject: Re: 8.0-RELEASE/amd64 - full ZFS install - low read and write disk performance 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: Sun, 24 Jan 2010 18:40:37 -0000 On Sun, Jan 24, 2010 at 8:34 PM, Jason Edwards wrote: >> ZFS writes to a mirror pair >> requires two independent writes. =A0If these writes go down independent = I/O >> paths, then there is hardly any overhead from the 2nd write. =A0If the >> writes >> go through a bandwidth-limited shared path then they will contend for th= at >> bandwidth and you will see much less write performance. > > What he said may confirm my suspicion on PCI. So if you could try the sam= e > with "real" Serial ATA via chipset or PCI-e controller you can confirm th= is > story. I would be very interested. :P > > Kind regards, > Jason This wouldn't explain why ZFS mirror on 2 disks directly, on the exact same controller (with the OS running off a separate disks) results in "expected" performance, while having the OS run off/on a ZFS mirror running on top of MBR-partitioned disks, on the same controller, results in very low speed. - Dan