From owner-freebsd-stable@FreeBSD.ORG Fri May 10 10:24:04 2013 Return-Path: Delivered-To: freebsd-stable@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 6A7D75B5 for ; Fri, 10 May 2013 10:24:04 +0000 (UTC) (envelope-from ronald-freebsd8@klop.yi.org) Received: from smarthost1.greenhost.nl (smarthost1.greenhost.nl [195.190.28.78]) by mx1.freebsd.org (Postfix) with ESMTP id 05715F72 for ; Fri, 10 May 2013 10:24:03 +0000 (UTC) Received: from smtp.greenhost.nl ([213.108.104.138]) by smarthost1.greenhost.nl with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.69) (envelope-from ) id 1UakFP-0004UC-FK for freebsd-stable@freebsd.org; Fri, 10 May 2013 12:08:20 +0200 Received: from dhcp-077-251-158-153.chello.nl ([77.251.158.153] helo=ronaldradial) by smtp.greenhost.nl with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1UakFN-0001cc-MK for freebsd-stable@freebsd.org; Fri, 10 May 2013 12:08:17 +0200 Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes To: freebsd-stable@freebsd.org Subject: Re: recommended memory for zfs References: <518BA237.3030700@gmail.com> <518C450B.5070809@ShaneWare.Biz> <518C51AF.5050609@gmail.com> <20130510020628.GA98750@icarus.home.lan> <518C5902.5050909@gmail.com> Date: Fri, 10 May 2013 12:08:17 +0200 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Ronald Klop" Message-ID: In-Reply-To: <518C5902.5050909@gmail.com> User-Agent: Opera Mail/12.15 (Win32) X-Virus-Scanned: by clamav at smarthost1.samage.net X-Spam-Level: / X-Spam-Score: 0.8 X-Spam-Status: No, score=0.8 required=5.0 tests=BAYES_50 autolearn=disabled version=3.3.1 X-Scan-Signature: 67ca9281b58cf5c8a5b2b1d981559170 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 10 May 2013 10:24:04 -0000 On Fri, 10 May 2013 04:18:42 +0200, Benjamin Adams wrote: > On 05/09/2013 10:06 PM, Jeremy Chadwick wrote: >> On Thu, May 09, 2013 at 09:47:27PM -0400, Benjamin Adams wrote: >>> On 05/09/2013 08:53 PM, Shane Ambler wrote: >>>> On 09/05/2013 22:48, Benjamin Adams wrote: >>>>> Hello zfs question about memory. >>>>> I heard zfs is very ram hungry. >>>>> Service looking to run: >>>>> - nginx >>>>> - postgres >>>>> - php-fpm >>>>> - python >>>>> >>>>> I have a machine with two quad core cpus but only 4 G Memory >>>>> >>>>> I'm looking to buy more ram now. >>>>> What would be the recommend amount of memory for zfs across 6 drives >>>>> on >>>>> this setup? >>>>> >>>> I believe I heard a calculation of 1GB cache per 1TB of disk. But >>>> basically zfs will use all free ram available if you access that >>>> much data from disk. You will want to set vfs.zfs.arc_max to allow >>>> enough ram for your apps to work in. >>>> >>>> If you consider the files for your website and the data you store >>>> you may find that you would never fill more than 500MB of cache. >>>> >>>> If you will be serving large media files that will easily use up >>>> the cache you could give them their own filesystem that only >>>> caches metadata - zfs set primarycache=metadata zroot/mediafiles >>>> >>>> >>> Thanks for all the replies Size of DB and HD's are: >>> >>> Current DB Size = 23 GB >>> HD sizes = (6) 500 GB drives >> Nobody is going to be able to give you a precise/accurate recommendation >> given the lack of detail provided, I'm sorry to say. What's the RES >> size of nginx (all processes combined)? What's the RES size of >> postgres (same)? Do you have PHP scripts that "run amok" for long >> periods of time and take up lots of RAM? Same with python? How many >> concurrent visitors and what sort of content are you hosting? Do you >> maintain/write your own PHP/Python code or are you using some crap like >> Wordpress? >> >> This is just a **small** list of questions -- and what may come as a >> shock is that I do not expect you to provide answers to any of them. >> They are questions that you should, for yourself, attempt to answer and >> work out what you need from there ("teach a man to fish" and all that). >> >> The advice of "1GB of RAM per 1TB of disk space" is absolute nonsense on >> numerous levels -- whoever gave this advice to Shane either has no >> understanding of how filesystems/ZFS works, or does but chose to >> simplify to the point where they're providing half-ass information. >> There is no direct, or even indirect, correlation between disk capacity >> and ZFS ARC size -- what matter is your "working set" (to quote Tom). >> You need to have some idea of how much disk I/O you're doing, and what >> type of I/O (sequential or random). >> >> If you want my general advice, Benjamin, it's this: get yourself a >> system with *minimum* 8GB of RAM but has the physical possibility of >> supporting more (and only add more RAM when/if you know you need it); do >> not bother with ZFS on a system with 4GB. Run amd64, not i386 (I don't >> recommend bothering with ZFS on i386 -- I am not going to get into a >> discussion about this either). Run stable/9, not 9.1-RELEASE. Avoid >> compression and dedup. And test disk failures as well (don't get caught >> with your pants down later). >> >> The above advice comes from someone who did hosting (web/ssh/etc.) for >> almost 20 years with KISS principle applied at all levels. YMMV though, >> depending on what all you're doing/what you truly need. >> >> Good luck. >> > Jeremy, > > Was just see if I should just get raid controller and more ram down the > road. > List of priorities. > > Main thing is I move from BSD when 9.0 came out. Was looking to see if > zfs is included in the installer. Now. > > Sum up: > upgrade ram to 16GB (not 64 like plained) > and raid controller that supports level 5. > Let ZFS do the RAID stuff. Do not use a RAID controller, but give the plain disks to ZFS. Some of the nice features come from ZFS doing the RAID stuff. Ronald.