From owner-freebsd-questions@FreeBSD.ORG Sat May 25 15:45:00 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 539A379 for ; Sat, 25 May 2013 15:45:00 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: from mail-qc0-x22d.google.com (mail-qc0-x22d.google.com [IPv6:2607:f8b0:400d:c01::22d]) by mx1.freebsd.org (Postfix) with ESMTP id 145FC7AE for ; Sat, 25 May 2013 15:44:59 +0000 (UTC) Received: by mail-qc0-f173.google.com with SMTP id c11so2898958qcv.18 for ; Sat, 25 May 2013 08:44:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer :x-gm-message-state; bh=yI4y6lIDBnmDrOJxTk/XKPhCtUqhC60Pb26QNZIRAaM=; b=IF5F+cgVmIzsNsJMZbZi9Xf5wjXGY7uwZQXYGqfxEkXA2Rx6NZHhd0ecPSuVl/5Ea0 wCHk4O96/HmRG/oXX5yBEvOeqhoOp3Ks9eRw5FOaG2HYwn2OioJ4pGGZXuigXIjJPyp+ ZuCURn7KKURlfomvAiU9KNBFcfUNXyFEXqZDNH/oHF5qdFF/e9YmmgzG6WYYQe5j9lbR 9GoRC84lZp0kVFrlrITYq/VUAknJVQqozf8M6/2M9ODJCnfz6O6w7nKSt2rggn1n56E1 s+9YKVn9Sorl2C+dfqZnYZ7UVsQW/4WLFKuWhC+LmCQvtL8+U2MRtYAiJ0logzOgY6VN eWaQ== X-Received: by 10.49.39.68 with SMTP id n4mr23518505qek.44.1369496699390; Sat, 25 May 2013 08:44:59 -0700 (PDT) Received: from [172.30.5.204] (ip66-104-8-126.z8-104-66.customer.algx.net. [66.104.8.126]) by mx.google.com with ESMTPSA id do6sm19190875qab.12.2013.05.25.08.44.57 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 25 May 2013 08:44:58 -0700 (PDT) Subject: Re: file corruption solution (soft-update or ZFS) Mime-Version: 1.0 (Mac OS X Mail 6.3 \(1503\)) Content-Type: text/plain; charset=us-ascii From: Paul Kraus In-Reply-To: Date: Sat, 25 May 2013 11:44:59 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: <9F319856-E79D-49F5-A0C9-3650DDC0C740@kraus-haus.org> References: To: Michael Sierchio X-Mailer: Apple Mail (2.1503) X-Gm-Message-State: ALoCoQk0BZLiWE904dgsNmD6Fyxc/FqKyzNnNqTN6w3utrFrcu9P1dLFBBrI8Z6H8BcVTNwnmVvC Cc: saeedeh motlagh , freebsd-questions X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 25 May 2013 15:45:00 -0000 On May 23, 2013, at 11:09 AM, Michael Sierchio = wrote: > On Thu, May 23, 2013 at 5:33 AM, Warren Block = wrote: >=20 >> .. >=20 >> One thing mentioned earlier is that ZFS wants lots of memory. 4G-8G >> minimum, some might say as much as the server will hold. >>=20 >>=20 > Not necessarily so - deduplication places great demands on memory, but = that > can be satisfied with dedicated cache devices (on SSD for performance = and > safety reasons). Without dedup, the requirements are more modest. The rule of thumb for DeDupe is 1GB physical RAM for every 1TB of = capacity. The issue is that the DeDupe metadata table must live in the = ARC for good performance. The discussion I have seen on the ZFS lists = indicates that L2ARC is not really adequate for this, so adding cache = devices (SSD's) don't really help. On the other hand, you can use ZFS without DeDupe with as little as 2GB = of total system RAM (depending on what else the system is doing). In my = experience, the amount of RAM depends on the amount of I/O not the = amount of storage. I find between 1GB and 3GB space for the ARC is = adequate. -- Paul Kraus Deputy Technical Director, LoneStarCon 3 Sound Coordinator, Schenectady Light Opera Company