From owner-freebsd-fs@FreeBSD.ORG Wed Mar 27 12:06:03 2013 Return-Path: Delivered-To: freebsd-fs@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 5153C5F7 for ; Wed, 27 Mar 2013 12:06:03 +0000 (UTC) (envelope-from 000.fbsd@quip.cz) Received: from elsa.codelab.cz (elsa.codelab.cz [94.124.105.4]) by mx1.freebsd.org (Postfix) with ESMTP id 13B2D5E7 for ; Wed, 27 Mar 2013 12:06:02 +0000 (UTC) Received: from elsa.codelab.cz (localhost [127.0.0.1]) by elsa.codelab.cz (Postfix) with ESMTP id D44A52842A; Wed, 27 Mar 2013 13:05:55 +0100 (CET) Received: from [192.168.1.2] (ip-89-177-49-222.net.upcbroadband.cz [89.177.49.222]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by elsa.codelab.cz (Postfix) with ESMTPSA id 946A728422; Wed, 27 Mar 2013 13:05:54 +0100 (CET) Message-ID: <5152E0A3.1090507@quip.cz> Date: Wed, 27 Mar 2013 13:05:55 +0100 From: Miroslav Lachman <000.fbsd@quip.cz> User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.9.1.19) Gecko/20110420 Lightning/1.0b1 SeaMonkey/2.0.14 MIME-Version: 1.0 To: Zeus Panchenko Subject: Re: RAM amount recommendations for ZFS pools with ZIL and L2ARC on SSD References: <20130322172657.95912@relay.ibs.dn.ua> In-Reply-To: <20130322172657.95912@relay.ibs.dn.ua> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-fs@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 27 Mar 2013 12:06:03 -0000 Zeus Panchenko wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > hi all, > > while discovering the subj, I found recommendations at: > http://doc.freenas.org/index.php/Hardware_Recommendations#RAM > > - --------------------------------------------------------------------- > ... a general rule of thumb is 1 GB of RAM for every 1TB of storage ... > If you plan to use ZFS deduplication, a general rule of thumb is 5 GB > RAM per TB of storage to be deduplicated. > - --------------------------------------------------------------------- > > > so, are these recommendations correct for ZFS pools with ZIL and L2ARC > on SSD configurations? > > are there corellations between "RAM amount" and "with/without ZIL, L2ARC > on separate devices pool configuration" ? The bigger L2ARC you have, the more RAM you need to store metadata about "what is in L2ARC". So if you have some system without L2ARC and you will add SSD as L2ARC, then you will need more RAM than before. It depends on records size and number of records stored in L2ARC. You can take a look at this thread http://www.mail-archive.com/zfs-discuss@opensolaris.org/msg34674.html http://www.mail-archive.com/zfs-discuss@opensolaris.org/msg34677.html Miroslav Lachman