From owner-freebsd-questions@FreeBSD.ORG Wed Jul 17 09:51:20 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 194D687A for ; Wed, 17 Jul 2013 09:51:20 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: from mail-wg0-x234.google.com (mail-wg0-x234.google.com [IPv6:2a00:1450:400c:c00::234]) by mx1.freebsd.org (Postfix) with ESMTP id A3216C3 for ; Wed, 17 Jul 2013 09:51:19 +0000 (UTC) Received: by mail-wg0-f52.google.com with SMTP id b12so1573833wgh.7 for ; Wed, 17 Jul 2013 02:51:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=PMrZEhc7qnZwGFWNe/ncKDmf/rC4yvJ+jUV1JlJnOdc=; b=HTs+QH2HLTV+mWvNnLJxrIjMaiGWT2mfrVWqkt0uEDTHaJbl5bwrFh9JgC9PPAIsTj qFaxqdr5uuNJaX7JoKUfUFDj7WKtO7JiNgPEtvabSB55306iIWviMkdamCsdBSbqRdlP e7UsdnoWdi3t7qc9QuGci6oWdu1vNbo2Yaa4McYoCp+98mYA9UMCEgK3/61W8opOio8n HSZO5kJx+QsvhfGHYMEGtCcVk1jTy35sfpFsEzvwOgTXKC2EVlevIivhMAK9HfvcFmBg NrdNeWeypZOH3sEiO1IOMtBL2QPAaMNih/C83CHMPJEoOLnFW4RkX+r2x0g+nA/0n37e UKQA== MIME-Version: 1.0 X-Received: by 10.180.206.70 with SMTP id lm6mr15236870wic.50.1374054677899; Wed, 17 Jul 2013 02:51:17 -0700 (PDT) Received: by 10.216.68.137 with HTTP; Wed, 17 Jul 2013 02:51:17 -0700 (PDT) In-Reply-To: <51E51558.50302@ShaneWare.Biz> References: <4DFBC539-3CCC-4B9B-AB62-7BB846F18530@gmail.com> <976836C5-F790-4D55-A80C-5944E8BC2575@gmail.com> <51E51558.50302@ShaneWare.Biz> Date: Wed, 17 Jul 2013 10:51:17 +0100 Message-ID: Subject: Re: to gmirror or to ZFS From: krad To: Shane Ambler Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.14 Cc: FreeBSD Questions , aurfalien 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: Wed, 17 Jul 2013 09:51:20 -0000 You would in theory as from what i remember every zfs filesystem takes up 64 kb of ram, so the savings could be massive 8) On 16 July 2013 10:41, Shane Ambler wrote: > On 16/07/2013 14:41, aurfalien wrote: > >> >> On Jul 15, 2013, at 9:23 PM, Warren Block wrote: >> >> On Mon, 15 Jul 2013, aurfalien wrote: >>> >>> ... thats the question :) >>>> >>>> At any rate, I'm building a rather large 100+TB NAS using ZFS. >>>> >>>> However for my OS, should I also ZFS or simply gmirror as I've a >>>> dedicated pair of 256GB SSD drives for it. I didn't ask for SSD >>>> sys drives, this system just came with em. >>>> >>>> This is more of a best practices q. >>>> >>> >>> ZFS has data integrity checking, gmirror has low RAM overhead. >>> gmirror is, at present, restricted to MBR partitioning due to >>> metadata conflicts with GPT, so 2TB is the maximum size. >>> >>> Best practices... depends on your use. gmirror for the system >>> leaves more RAM for ZFS. >>> >> >> Perfect, thanks Warren. >> >> Just what I was looking for. >> > > I doubt that you would save any ram having the os on a non-zfs drive as > you will already be using zfs chances are that non-zfs drives would only > increase ram usage by adding a second cache. zfs uses it's own cache > system and isn't going to share it's cache with other system managed > drives. I'm not actually certain if the system cache still sits above > zfs cache or not, I think I read it bypasses the traditional drive cache. > > For zfs cache you can set the max usage by adjusting vfs.zfs.arc_max > that is a system wide setting and isn't going to increase if you have > two zpools. > > Tip: set the arc_max value - by default zfs will use all physical ram > for cache, set it to be sure you have enough ram left for any services > you want running. > > Have you considered using one or both SSD drives with zfs? They can be > added as cache or log devices to help performance. > See man zpool under Intent Log and Cache Devices. > > > ______________________________**_________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/**mailman/listinfo/freebsd-**questions > To unsubscribe, send any mail to "freebsd-questions-** > unsubscribe@freebsd.org " >