From owner-freebsd-hardware Tue Jan 4 8:11: 2 2000 Delivered-To: freebsd-hardware@freebsd.org Received: from benge.graphics.cornell.edu (benge.graphics.cornell.edu [128.84.247.43]) by hub.freebsd.org (Postfix) with ESMTP id F03991540D for ; Tue, 4 Jan 2000 08:10:46 -0800 (PST) (envelope-from mkc@benge.graphics.cornell.edu) Received: from benge.graphics.cornell.edu (mkc@localhost) by benge.graphics.cornell.edu (8.9.3/8.9.3) with ESMTP id LAA15549 for ; Tue, 4 Jan 2000 11:10:39 -0500 (EST) (envelope-from mkc@benge.graphics.cornell.edu) Message-Id: <200001041610.LAA15549@benge.graphics.cornell.edu> To: hardware@FreeBSD.ORG Subject: differences between SCSI and EIDE [was: wanna buy an EIDE harddisk ... 5400 or 7200 for home use (noise)] In-Reply-To: Message from Jonathan Michaels of "Tue, 04 Jan 2000 18:42:59 +1100." <20000104184258.A84552@phoenix.welearn.com.au> Date: Tue, 04 Jan 2000 11:10:39 -0500 From: Mitch Collinsworth Sender: owner-freebsd-hardware@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org >anyway, thank you all for responding and sheading light on my >confusion. i'd always thought that scsi was the better way to >go, either fro the 'comercial' environment or the ever more >demanding 'home' environment. Well this is actually an interesting question. My salesman says the HDAs are the same in SCSI and EIDE drives, so reliability-wise there should be no difference. So far I've stuck with SCSI but due to the significantly lower cost, management is pushing me to use EIDE where possible in the future. I'd like to know of any significant down-sides to using EIDE other than the number of devices per controller. I read on a seller's web page yesterday that: "EIDE is not well designed for preemptive multitasking. EIDE drives can not do more than one task at a time. In contrast, SCSI devices are handle more jobs and SCSI controllers can tag queue several commands." This page appears to have been written a few years ago, so I'm concerned the information may be dated. But assuming it is still accurate, I'd like to better understand what is being said here. Do SCSI device drivers typically initiate multiple commands from separate processes to the drive without waiting for the previous command to complete? In other words the drive logic has it's own queue management? And EIDE drives require their device drivers to perform all queue management and only initiate a command after the previous one has completed? Is the bottom line result of this that the SCSI drive has a much greater chance of servicing multiple processes during a single media revolution while the EIDE will frequently take multiple revolutions to service the same queue? -Mitch To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message