From owner-freebsd-scsi@FreeBSD.ORG Thu May 8 07:59:07 2014 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id EA4F1D58; Thu, 8 May 2014 07:59:07 +0000 (UTC) Received: from cu01176b.smtpx.saremail.com (cu01176b.smtpx.saremail.com [195.16.151.151]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id AA512BB2; Thu, 8 May 2014 07:59:06 +0000 (UTC) Received: from [172.16.2.2] (izaro.sarenet.es [192.148.167.11]) by proxypop04.sare.net (Postfix) with ESMTPSA id D97479DE3BB; Thu, 8 May 2014 09:49:03 +0200 (CEST) Subject: Re: Testing new mpr driver Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=us-ascii From: Borja Marcos In-Reply-To: <20140507184557.GA80243@nargothrond.kdm.org> Date: Thu, 8 May 2014 09:49:02 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <4DB83981-0D4D-4484-BC89-4ED8C02DCD0F@sarenet.es> References: <8A41AB90-AC2F-4200-91D6-3D3CF9E8A835@sarenet.es> <20140507184557.GA80243@nargothrond.kdm.org> To: Kenneth D. Merry X-Mailer: Apple Mail (2.1283) Cc: freebsd-scsi@freebsd.org X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 08 May 2014 07:59:08 -0000 On May 7, 2014, at 8:45 PM, Kenneth D. Merry wrote: > That's hard to say. If you're using a 6Gb expander, you would have = half of > the available SAS bandwidth if you only connected four lanes from the > controller to the expander instead of 8. If you somehow have a 12Gb > expander (it isn't obvious from the model number above what the = expander > speed is), then you would have the same amount of bandwidth. Anyway, as far as I understand (SAS expanders perform link switching, = right?) the actual speed will be limited by the end to end speed. As the disks I am using are SATA, not SAS, each = lane would be anyway working at=20 6 Gbps instead of 12.=20 > One thing that could be happening is you may have lower latency = through the > new 12Gb controller. As I saw it supports something called "fastpath" (I must read something, = I am a bit outdated in these matters) I imagined that it=20 might be a more efficient transfer method which, despite working at 6 = Gbps, might explain a gain in performance. > By the way, if you run with INVARIANTS enabled, you may run into some > issues (i.e. a panic) on reboot until we merge r265485 to stable/10. I am running stable/10, and I'm not running INVARIANTS. Anyway I will = be tracking stable/10 closely, thank you! Great to have LSI so seriously involved! Borja.