From owner-freebsd-performance@FreeBSD.ORG Wed May 6 19:21:56 2009 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id DD8E01065693; Wed, 6 May 2009 19:21:55 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (gate6.infracaninophile.co.uk [IPv6:2001:8b0:151:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id 5D3188FC2A; Wed, 6 May 2009 19:21:55 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from happy-idiot-talk.infracaninophile.co.uk (localhost [IPv6:::1]) (authenticated bits=0) by smtp.infracaninophile.co.uk (8.14.3/8.14.3) with ESMTP id n46JLjhf002316; Wed, 6 May 2009 20:21:46 +0100 (BST) (envelope-from m.seaman@infracaninophile.co.uk) X-DKIM: Sendmail DKIM Filter v2.8.2 smtp.infracaninophile.co.uk n46JLjhf002316 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=infracaninophile.co.uk; s=200708; t=1241637707; bh=Jl9iT116utVryz/yVoKH9Ycx4vi1/dRMC6BdjU1Bvn4=; 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<4A01E343.4020608@infracaninophile.co.uk>|Date:=20W ed,=2006=20May=202009=2020:21:39=20+0100|From:=20Matthew=20Seaman= 20|Organization:=20Infracaninophi le|User-Agent:=20Thunderbird=202.0.0.21=20(X11/20090420)|MIME-Vers ion:=201.0|To:=20Gary=20Gatten=20|CC:=20freeb sd-performance@freebsd.org,=20freebsd-questions@freebsd.org|Subjec t:=20Re:=20filesystem:=2012h=20to=20delete=2032GB=20of=20data|Refe rences:=20<70C0964126D66F458E688618E1CD008A0793EBD4@WADPEXV0.wadde ll.com>|In-Reply-To:=20<70C0964126D66F458E688618E1CD008A0793EBD4@W ADPEXV0.waddell.com>|X-Enigmail-Version:=200.95.6|Content-Type:=20 multipart/signed=3B=20micalg=3Dpgp-sha256=3B=0D=0A=20protocol=3D"a pplication/pgp-signature"=3B=0D=0A=20boundary=3D"------------enigD 7935878E099234D25665A93"; b=O/hp7luaPoCu2nJB2HIvnhkwnwWnldUymDndQQOw8eOMC3vBzY1aNGZl6ednKAS+e efA1tzCqc+2+Rqd90abJlam3946weQ0hzkxb4J/v6asi3N4bfq73iB3H5B9doDKMo7 0o2idp2vxpEmozGavC/krcdGE/3jdDQI8EtgkG9c= X-Authentication-Warning: happy-idiot-talk.infracaninophile.co.uk: Host localhost [IPv6:::1] claimed to be happy-idiot-talk.infracaninophile.co.uk Message-ID: <4A01E343.4020608@infracaninophile.co.uk> Date: Wed, 06 May 2009 20:21:39 +0100 From: Matthew Seaman Organization: Infracaninophile User-Agent: Thunderbird 2.0.0.21 (X11/20090420) MIME-Version: 1.0 To: Gary Gatten References: <70C0964126D66F458E688618E1CD008A0793EBD4@WADPEXV0.waddell.com> In-Reply-To: <70C0964126D66F458E688618E1CD008A0793EBD4@WADPEXV0.waddell.com> X-Enigmail-Version: 0.95.6 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigD7935878E099234D25665A93" X-Virus-Scanned: clamav-milter 0.95.1 at happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-3.0 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VERIFIED,NO_RELAYS autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on happy-idiot-talk.infracaninophile.co.uk Cc: freebsd-performance@freebsd.org, freebsd-questions@freebsd.org Subject: Re: filesystem: 12h to delete 32GB of data X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 May 2009 19:21:58 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD7935878E099234D25665A93 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Gary Gatten wrote: > OT now, but in high i/o envs with high concurrency needs, RAID5 is > still the way to go, esp if 90% of i/o is reads. Of course it depends > on file size / type as well... Anyway, let's sum it up with "a > storage subsystem is only as fast as its slowest link" It's not just the balance of reads over writes. It's the size and sequen= tial location of the IO requests. RAID5 is good for sequential reads -- eg. streaming a video -- where the system can read whole blocks from all the drives involved, calculate parity over the whole lot and then push all th= at blob of data up to the CPU. RAID5 is pretty pessimal if your usage pattern is small reads or writes randomly scattered over your storage area -- eg. typical RDBMS behaviour -- which works a great deal better on RAID10. I'd also contend that the essential difference between a really good fast= hardware raid controller and something disappointingly mundane is a decen= t amount of non-volatile cache memory. For most H/W raid that equates to using a battery backup unit. I've been thinking though that a few GB of fast solid-state hard drive configured as a gjournal for a RAID10 (ie gst= ripe +gmirror) might achieve the same effect for rather less outlay... It would probably not be too shabby with RAID5 even, but of course you'ld lose the benefit of offloading parity calculations onto the RAID controll= er's CPU. Still, modern multi-core CPUs are probably fast enough nowadays to make that viable for many purposes. =20 Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigD7935878E099234D25665A93 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.11 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEAREIAAYFAkoB40kACgkQ8Mjk52CukIxlQwCfZUK2JDHgQBeZ+hAkCZImW2pO SkEAoIyWUGFD7u0sDmqjueBr6w6TokAG =zm6f -----END PGP SIGNATURE----- --------------enigD7935878E099234D25665A93--