From owner-freebsd-stable@FreeBSD.ORG Mon Mar 21 09:47:17 2011 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 36612106566C for ; Mon, 21 Mar 2011 09:47:17 +0000 (UTC) (envelope-from srg.gavrilov@gmail.com) Received: from mail-iw0-f182.google.com (mail-iw0-f182.google.com [209.85.214.182]) by mx1.freebsd.org (Postfix) with ESMTP id EE6AA8FC19 for ; Mon, 21 Mar 2011 09:47:16 +0000 (UTC) Received: by iwn33 with SMTP id 33so7346820iwn.13 for ; Mon, 21 Mar 2011 02:47:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=uVj1AHGg3pCLFxpjIpOPwFoNkthTYz1oVt2N2K0VEq0=; b=pLGR2q1YFrcdQskmcTJy4BcHb7MG8UqMlztNZQZbvrleWgg3C2C8G2GT0WJn9Qm83W y+mVCYQ8Zf8f7IM6tmjGp5g1OOXby6y6IdNjviqE+8Qpz4MaDd7p7ZbYURAS2DhaE4JH Qr7k4odSrpQMUU9pcFsRQ4jsBOMP66w6kDJq8= 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 :cc:content-type; b=I+flGcF4wbLFOsrT4CAZfHJswHUhCTf47/ggb10FmDsUsZHX4lTU89f63nhUcDVgFb GcQzPLuuhY4cvZjN2vnSlMB0dvspk7bP1yu1DPMnWk+u/faHvZk76AvRa5w+ji4Q/BAA LcQg92HLONliQWfwuwjIqtyahP3e1TwsYk5Ak= MIME-Version: 1.0 Received: by 10.43.59.207 with SMTP id wp15mr4157232icb.163.1300700836347; Mon, 21 Mar 2011 02:47:16 -0700 (PDT) Received: by 10.42.217.66 with HTTP; Mon, 21 Mar 2011 02:47:16 -0700 (PDT) In-Reply-To: References: <4D660909.6090202@my.gd> <20110224075517.GA18146@icarus.home.lan> Date: Mon, 21 Mar 2011 12:47:16 +0300 Message-ID: From: Sergey Gavrilov To: Paul Mather Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-stable@freebsd.org Subject: Re: ZFS - abysmal performance with samba since upgrade to 8.2-RELEASE 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, 21 Mar 2011 09:47:17 -0000 Yes, I know. But I have a lot of memory and I want it to be used if it improves performance. I tried to test whole system not just fs. And I surprised in why vfs.zfs.prefetch_disable="1" affects so much. 2011/3/18 Paul Mather > > On Mar 18, 2011, at 5:53 AM, Sergey Gavrilov wrote: > > > vfs.zfs.prefetch_disable="1" causes much slow read on sequence data in my > > case. > > > > with vfs.zfs.prefetch_disable="1": > > > > dd if=/pool1/test/idisk1 of=/dev/null bs=1m count=500 > > 524288000 bytes transferred in 18.347177 secs (28575949 bytes/sec) > > > > with vfs.zfs.prefetch_disable="0": > > > > dd if=/pool1/test/idisk1 of=/dev/null bs=1m count=500 > > 524288000 bytes transferred in 3.331806 secs (157358504 bytes/sec) > > > > after few seconds: > > dd if=/pool1/test/idisk1 of=/dev/null bs=1m count=500 > > 524288000 bytes transferred in 0.107767 secs (4865009592 bytes/sec) > > The last dd performance figures are undoubtedly reflecting a read from data > cached in RAM. You should do your test on a file that is bigger than your > RAM size, or at least bigger than the amount of RAM you are dedicating to > ARC. > > Other than that, ZFS prefetching *is* supposed to speed up sequential > accesses, so it's no surprise you notice a speedup in such cases. :-) > > Cheers, > > Paul. > > -- Best regards, Sergey Gavrilov