From owner-freebsd-questions@FreeBSD.ORG Mon Mar 15 23:40:28 2010 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 E421C1065672; Mon, 15 Mar 2010 23:40:27 +0000 (UTC) (envelope-from dan.naumov@gmail.com) Received: from mail-bw0-f228.google.com (mail-bw0-f228.google.com [209.85.218.228]) by mx1.freebsd.org (Postfix) with ESMTP id 5254B8FC15; Mon, 15 Mar 2010 23:40:26 +0000 (UTC) Received: by bwz28 with SMTP id 28so3492174bwz.14 for ; Mon, 15 Mar 2010 16:40:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:date:message-id:subject :from:to:content-type; bh=kTezEwnvGUoxTWT6csQjE9+sfxcsj4bUFE4BKr/SOJA=; b=G9qUDKl+RNf6gE12OzMuHmrrp5q2mzDj9bg6RiFJTOSMsIqO6FJUzj+g2dHNN7OdLH 4AABzaZao7VtAHG8IQuo8UMbdv7P/Os0YtnMK3dcW7SjmXKW3cmdFfM+5I1HzrsrxV8n 5iVouwAfYLciOkbqzOSeowfD2HRk1cuPJMlG8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=VXeFv0eZhdwFfc8AFtUi6yDzWUNqMnrMVC7Wiag/SSwRXc6AcTaE1/1XaRa3+d7D00 YCHgCf9qkQ/NYjHwzkeDc0kW6pq8dGWa12CKMBCHI3rNrGIMmneJ1LcOChYuRg979bsw TdDEiXsccs+lQUDRg8wFajMSsUCcx2WxMOeRs= MIME-Version: 1.0 Received: by 10.204.141.9 with SMTP id k9mr747685bku.73.1268696425833; Mon, 15 Mar 2010 16:40:25 -0700 (PDT) Date: Tue, 16 Mar 2010 01:40:25 +0200 Message-ID: From: Dan Naumov To: freebsd-questions@freebsd.org, freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Cc: Subject: Some questions about vfs.zfs.prefetch_disable=1 and ZFS filesystem versions X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 15 Mar 2010 23:40:28 -0000 After looking at the arc_summary.pl script (found at http://jhell.googlecode.com/files/arc_summary.pl), I have realized that my system has set vfs.zfs.prefetch_disable=1 by default, looking at dmesg, I see: ========================= ZFS NOTICE: Prefetch is disabled by default if less than 4GB of RAM is present; to enable, add "vfs.zfs.prefetch_disable=0" to /boot/loader.conf. ========================= ...except I do have 4gb of RAM. Is this caused by integrated GPU snatching some of my memory at boot? From dmesg: ========================= real memory = 4294967296 (4096 MB) avail memory = 4088082432 (3898 MB) ========================= What kind of things does this tunable affect and how much of a performance impact does enabling / disabling it have? Should I manually enable it? I've also noticed a really weird inconsistency, my dmesg says the following: ========================= ZFS filesystem version 13 ZFS storage pool version 13 ========================= Yet: ========================= zfs get version NAME PROPERTY VALUE SOURCE cerberus version 3 - cerberus/DATA version 3 - cerberus/ROOT version 3 - cerberus/ROOT/cerberus version 3 - cerberus/home version 3 - cerberus/home/atombsd version 3 - cerberus/home/friction version 3 - cerberus/home/jago version 3 - cerberus/home/karni version 3 - cerberus/tmp version 3 - cerberus/usr-local version 3 - cerberus/usr-obj version 3 - cerberus/usr-ports version 3 - cerberus/usr-ports-distfiles version 3 - cerberus/usr-src version 3 - cerberus/var version 3 - cerberus/var-db version 3 - cerberus/var-log version 3 - cerberus/var-tmp version 3 - ========================= Is this normal or should "zfs get version" also show version 13? This is on a system with the pool and filesystems created with 8.0-RELEASE, by the way. Thanks! - Sincerely, Dan Naumov