From owner-freebsd-questions@FreeBSD.ORG Wed Sep 14 18:51:24 2011 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D2DD1106564A for ; Wed, 14 Sep 2011 18:51:24 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (smtp6.infracaninophile.co.uk [IPv6:2001:8b0:151:1:3fd3:cd67:fafa:3d78]) by mx1.freebsd.org (Postfix) with ESMTP id 44BE28FC0A for ; Wed, 14 Sep 2011 18:51:24 +0000 (UTC) Received: from seedling.black-earth.co.uk (seedling.black-earth.co.uk [81.187.76.163]) (authenticated bits=0) by smtp.infracaninophile.co.uk (8.14.5/8.14.5) with ESMTP id p8EIpE1U038964 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Wed, 14 Sep 2011 19:51:20 +0100 (BST) (envelope-from m.seaman@infracaninophile.co.uk) X-DKIM: Sendmail DKIM Filter v2.8.3 smtp.infracaninophile.co.uk p8EIpE1U038964 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=infracaninophile.co.uk; s=201001-infracaninophile; t=1316026280; bh=QE77antiX+YUtz9iFBfAcWFHD6SIBqMxliVJzFeksNM=; h=Message-ID:Date:From:MIME-Version:To:CC:Subject:References: In-Reply-To:Content-Type:Cc:Content-Type:Date:From:In-Reply-To: Message-ID:Mime-Version:References:To; z=Message-ID:=20<4E70F79A.3090806@infracaninophile.co.uk>|Date:=20W ed,=2014=20Sep=202011=2019:51:06=20+0100|From:=20Matthew=20Seaman= 20|User-Agent:=20Mozilla/5.0=20(M acintosh=3B=20Intel=20Mac=20OS=20X=2010.6=3B=20rv:6.0.2)=20Gecko/2 0110902=20Thunderbird/6.0.2|MIME-Version:=201.0|To:=20Michael=20Si erchio=20|CC:=20Jonathan=20Vomacka=20,=20freebsd-questions@freebsd.org|Subject:=20Re:=20Recom mended=20SWAP=20space=20for=20large=20amounts=20of=20ram=20(8GB)|R eferences:=20<4E709F62.60705@gmail.com>=20<4E70B269.4020900@infrac aninophile.co.uk>=20|In-Reply-To:=20|X-Enigmail-Versio n:=201.3.1|OpenPGP:=20id=3D60AE908C|Content-Type:=20multipart/sign ed=3B=20micalg=3Dpgp-sha1=3B=0D=0A=20protocol=3D"application/pgp-s ignature"=3B=0D=0A=20boundary=3D"------------enigFA081D3548B0033F9 C0CCC4C"; b=r7Wiqn52YSnn/HgLRCcGOpndGoz5YPw6AYiRyYmQW/KYMxN6EIFjQ3z0j0rFiuNuI 2AyDCnoenaVbF76l0UKVblJqguD807YFxiLy7H8X5XaTXAKRfzlUa3u1pdlrpWjxMN JifuFdik85kQ+gc0EM8/3jhLIaAaKfsRAjp8QdkA= Message-ID: <4E70F79A.3090806@infracaninophile.co.uk> Date: Wed, 14 Sep 2011 19:51:06 +0100 From: Matthew Seaman User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:6.0.2) Gecko/20110902 Thunderbird/6.0.2 MIME-Version: 1.0 To: Michael Sierchio References: <4E709F62.60705@gmail.com> <4E70B269.4020900@infracaninophile.co.uk> In-Reply-To: X-Enigmail-Version: 1.3.1 OpenPGP: id=60AE908C Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigFA081D3548B0033F9C0CCC4C" X-Virus-Scanned: clamav-milter 0.97.2 at lucid-nonsense.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=0.7 required=5.0 tests=BAYES_50,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU autolearn=ham version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on lucid-nonsense.infracaninophile.co.uk Cc: Jonathan Vomacka , freebsd-questions@freebsd.org Subject: Re: Recommended SWAP space for large amounts of ram (8GB) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Sep 2011 18:51:24 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigFA081D3548B0033F9C0CCC4C Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 14/09/2011 18:27, Michael Sierchio wrote: > On Wed, Sep 14, 2011 at 6:55 AM, Matthew Seaman > wrote: >=20 >> > ... In these days of plentiful RAM, the new rule of thumb is "if you= 're >> > swapping, then you're doing it wrong." > I think your response follows the excellent pedagogical principle: "a > little inaccuracy saves a lot of explanation." But... disk is still > (by far) the cheapest commodity, and the opportunistic paging > algorithm manages VM very well. VM is not by any means obsolete, and > seeing paging behavior is not a sign of a misconfigured system. Well, yes. I was certainly glossing over a lot of complexity -- but I would maintain that I am fundamentally correct. Having some pages swapped out is absolutely not a problem. True. In fact, it's a positive benefit: swapping out memory pages that are exceedingly rarely referenced makes more room in RAM for more actively used pages. On the other hand, having pages continually swapping in and out definitely is a problem in terms of performance, given that disk IO takes of the order of milliseconds, while reference to main RAM is of the order of microseconds or less. Orders of magnitude faster. Now, while disk may well be the much the cheapest storage medium available, that's only part of the expense. In fact, up-front capital expenditure on the kit (perhaps several thousand pounds/euros/dollars) is outweighed by the operational expense (power, cooling, hardware support etc.) over the life of the equipment, so spending a bit more (capex) on components that run at lower power (opex) makes a lot of sense. Even more, if the server is being used for eg. e-Commerce, then the volume of the transactions and the data processed by the server makes all the difference to your margin: the more you can do with the same hardware - viz, the more efficiently and faster you can make the hardware run - then the more profit you make. Buying more RAM is peanuts on that scale. Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate JID: matthew@infracaninophile.co.uk Kent, CT11 9PW --------------enigFA081D3548B0033F9C0CCC4C Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.16 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk5w96IACgkQ8Mjk52CukIxIhgCdHpcHs3jMkJ2ZxiP8rBBP3Kp1 gKEAn2NLULVNc2fcGaY9/lSCPnkNXVlv =dGy2 -----END PGP SIGNATURE----- --------------enigFA081D3548B0033F9C0CCC4C--