From owner-freebsd-current@FreeBSD.ORG Tue May 30 17:44:49 2006 Return-Path: X-Original-To: current@FreeBSD.org Delivered-To: freebsd-current@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id EEFB516A944; Tue, 30 May 2006 17:44:48 +0000 (UTC) (envelope-from brdavis@odin.ac.hmc.edu) Received: from odin.ac.hmc.edu (Odin.AC.HMC.Edu [134.173.32.75]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7C35B43D48; Tue, 30 May 2006 17:44:44 +0000 (GMT) (envelope-from brdavis@odin.ac.hmc.edu) Received: from odin.ac.hmc.edu (localhost.localdomain [127.0.0.1]) by odin.ac.hmc.edu (8.13.0/8.13.0) with ESMTP id k4UHiiOj016976; Tue, 30 May 2006 10:44:44 -0700 Received: (from brdavis@localhost) by odin.ac.hmc.edu (8.13.0/8.13.0/Submit) id k4UHihQP016975; Tue, 30 May 2006 10:44:43 -0700 Date: Tue, 30 May 2006 10:44:43 -0700 From: Brooks Davis To: Robert Watson Message-ID: <20060530174443.GC6706@odin.ac.hmc.edu> References: <447AB34C.4030509@sippysoft.com> <11410450515.20060529225555@lacave.net> <447B77AF.9060309@samsco.org> <447B7A55.7040704@FreeBSD.org> <447B7CB7.5000000@FreeBSD.org> <447B8900.4050603@samsco.org> <20060530004328.GF28128@groat.ugcs.caltech.edu> <20060530015234.GB26022@odin.ac.hmc.edu> <20060530094413.W79162@fledge.watson.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="hYooF8G/hrfVAmum" Content-Disposition: inline In-Reply-To: <20060530094413.W79162@fledge.watson.org> User-Agent: Mutt/1.4.1i X-Virus-Scanned: by amavisd-new Cc: Paul Allen , "current@freebsd.org" , gallatin@FreeBSD.org Subject: Re: Importing iSCSI target from NetBSD X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 30 May 2006 17:44:59 -0000 --hYooF8G/hrfVAmum Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, May 30, 2006 at 09:46:39AM +0100, Robert Watson wrote: >=20 > On Mon, 29 May 2006, Brooks Davis wrote: >=20 > >On Mon, May 29, 2006 at 05:43:28PM -0700, Paul Allen wrote: > >>>From Scott Long , Mon, May 29, 2006 at 05:51:28PM= =20 > >>>-0600: > >>>>P.S. Just to make it clear - just consider running iSCSI over 100MBps > >>>>link or even a slower WAN links, which I think covers very large mark= et > >>>>for this technology now. Performance constrain imposed by running in > >>>>userland is unlikely to be an issue at all. > >>> > >>>Every company and group that I've talked to about iSCSI is worried abo= ut=20 > >>>performance. In any case, please follow the lead of Mr. Senault and= =20 > >>>look at making this a port. > >> > >>And in particular the anticipation of low(er) cost 10Gb Ethernet is a= =20 > >>driving factor behind iSCSI. > >> > >>AFAIK, the low-latency performer in this field (for NICs) is from=20 > >>Myricom. Andrew Gallatin (one of the FreeBSD alpha committers) was=20 > >>responsible for porting the myrinet drivers, so perhaps he can comment = as=20 > >>to whether FreeBSD will be getting a driver for their 10GbE cards. =20 > >>Ethernet at these speeds is real stress-test for many OSs; it should be= =20 > >>interesting to see how FreeBSD holds-up. > > > >There's a driver in current. We don't perform nearly as well as we shou= ld=20 > >at the moment. >=20 > FYI, I recently received donated hardware from Yahoo! and Drew has kindly= =20 > offered to send me a couple of 10gbps cards to work with, so I hope to ha= ve=20 > a chance to start doing some measurement and optimization work. One of t= he=20 > problems we've been having is that it's hard to optimize the CPU use of t= he=20 > network stack when the CPU significantly outstrips available bus and=20 > network bandwidth. It seems like hardware swings back and forth quite a= =20 > bit -- for a few years gigabit was way-the-heck-faster-than-CPU, now it's= =20 > the other way around again. The best stack optimization work happens whe= n=20 > you have to figure out how to get the network stack to perform well in=20 > near-infinite bandwidth scenarios with a CPU-bound stack, which is where = we=20 > are with 10gbps currently. One of the things that makes all this rather= =20 > tricky is that it's quite hard to build test rigs, test setups, and get t= he=20 > hardware details right. Hopefully, with Yahoo's and Drew's help, my test= =20 > setup will be good for looking at this for a couple of years. That's great news. This problem of relative performance leapfrogging is a pain. -- Brooks --=20 Any statement of the form "X is the one, true Y" is FALSE. 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