From owner-freebsd-stable@FreeBSD.ORG Wed Mar 9 13:28:52 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 7A8721065673 for ; Wed, 9 Mar 2011 13:28:52 +0000 (UTC) (envelope-from tevans.uk@googlemail.com) Received: from mail-qy0-f182.google.com (mail-qy0-f182.google.com [209.85.216.182]) by mx1.freebsd.org (Postfix) with ESMTP id 30B718FC26 for ; Wed, 9 Mar 2011 13:28:52 +0000 (UTC) Received: by qyk27 with SMTP id 27so389738qyk.13 for ; Wed, 09 Mar 2011 05:28:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=MglkwsWyCBVXtLIX8HERvKH7cMSXV7L6zXeZq6SITlg=; b=PhAIiufpCy8oy96wn3pfMuhlnoy2qffnd/5VEe7NcQHsWD6AyfUL8irQGobIMPQthK eDl+uytlxNxSbD6S6/+XhczgtEWJmSHdRVFH7kpmrGIytm6XWrhFqUQlCFLi256qy6L4 zaiwutYtUBFZdzgeV4p7xAIV+UC7B/rpPgegg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=q3rBcnnSKfSWxsCyVK6s2FY2PG+YkY2vRLSpMKJu7OYfZoDU4mmPK2jYcgqSR/qLZh fttdC/nF4iQW89Z0ojWvDzXPKWOW8YLqAvd9g3fgZ8gnjiPpwcKXCJmykujPbjwTjxHv 12PQHcsqTvuyaDZWOZn6iuJi+sFvdMBDTUtgk= MIME-Version: 1.0 Received: by 10.224.135.95 with SMTP id m31mr1388550qat.90.1299677330512; Wed, 09 Mar 2011 05:28:50 -0800 (PST) Received: by 10.229.79.139 with HTTP; Wed, 9 Mar 2011 05:28:50 -0800 (PST) In-Reply-To: <20110309125132.GB62338@icarus.home.lan> References: <20110308114810.GA37554@icarus.home.lan> <4D775CF1.1010501@gmx.de> <20110309125132.GB62338@icarus.home.lan> Date: Wed, 9 Mar 2011 13:28:50 +0000 Message-ID: From: Tom Evans To: Jeremy Chadwick Content-Type: text/plain; charset=UTF-8 Cc: Matthias Andree , freebsd-stable@freebsd.org Subject: Re: ZFS performance as the FS fills up? 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: Wed, 09 Mar 2011 13:28:52 -0000 On Wed, Mar 9, 2011 at 12:51 PM, Jeremy Chadwick wrote: > > Otherwise, I can imagine that prefetching could cause what you describe, > which is enabled by default in 8.0 and 8.1 and auto-disables in 8.2 if > the amount of available memory is less than 4GB. > I don't think this is accurate. Prefetch was certainly disabled by default on 8.0 if you had 4GB of RAM or less, requiring the sysctl vfs.zfs.prefetch_disable=0 to be set if you wanted prefetch and had 4GB of RAM or less. Cheers Tom