From owner-freebsd-questions Tue Jan 29 6:26:47 2002 Delivered-To: freebsd-questions@freebsd.org Received: from smtpproxy2.mitre.org (smtpproxy2.mitre.org [128.29.154.90]) by hub.freebsd.org (Postfix) with ESMTP id 8B28637B400 for ; Tue, 29 Jan 2002 06:26:41 -0800 (PST) Received: from avsrv2.mitre.org (avsrv2.mitre.org [128.29.154.4]) by smtpproxy2.mitre.org (8.11.3/8.11.3) with ESMTP id g0TEQcc08694; Tue, 29 Jan 2002 09:26:38 -0500 (EST) Received: from MAILHUB1 (mailhub1.mitre.org [129.83.20.31]) by smtpsrv2.mitre.org (8.11.3/8.11.3) with ESMTP id g0TEQbi27109; Tue, 29 Jan 2002 09:26:37 -0500 (EST) Received: from dhcp-105-164.mitre.org (128.29.105.164) by mailhub1.mitre.org with SMTP id 8996947; Tue, 29 Jan 2002 09:25:59 -0500 Message-ID: <3C56B11C.2C8CB6A7@mitre.org> Date: Tue, 29 Jan 2002 09:26:36 -0500 From: Jason Andresen Organization: The MITRE Corporation X-Mailer: Mozilla 4.75 [en]C-20000818M (Windows NT 5.0; U) X-Accept-Language: en MIME-Version: 1.0 To: ptiJo Cc: freebsd-questions@freebsd.org Subject: Re: divers SCSI questions... References: <20020128230531.20f8d55b.ptiJo@noos.fr> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG ptiJo wrote: > > Hi, > > as I never played with SCSI and get an old PCI Card, I would like to be enlightened a bit :) > so, I got the "Adaptec AHA-2940UW" which specs are: Ok, this is a slightly older but perfectly good card. > Computer Bus: > PCI Local Bus > Interface Protocol: > Bus master DMA > Host Bus Burst Data Rate: > 133 MByte/sec > Peripheral Bus: > 8-bit and 16-bit Wide UltraSCSI > SCSI Synchronous Data Rate: > 40 MByte/sec > SCSI Asynchronous Data Rate: > 3.3 MByte/sec > Device Protocol: > SCSI-1, SCSI-2, SCSI-3, Wide UltraSCSI > Device Support: > Up to 15 devices under DOS 5.0 and above > > Here are the questions :) > -1- does the data rates specify that, in general, the transfer rate is 3.3 MBytes/sec ? In general you will get 40MByte/sec with your drives (well, peak at least), at least with the drives listed below. SCSI has several different speeds, with different names. Your card supports 40 MB/S (SCSI-II Ultra Wide IIRC). The hard drives below are capable of 160MB/S (SCSI-III LVD). Since the limiting factor is your card you will get 40MBs throughput. > -2- 15 devices under DOS... would it be more under FreeBSD ? is there also a limitation on total size that I would get (15*36Go or 15*9Go, for eg) ? 15 devices is a SCSI limitation, and that's only for the newer SCSI's (old SCSI was limited to 7). Technically it's actually 16 devices, but the SCSI card itself counts as a device. > I would like to buy disks now :) > IBM 36 Go 10000 RPM SCSI > IBM 18 Go 10000 RPM SCSI > IBM 9 Go 10000 RPM SCSI > > -3- do I have to take special care ? I mean, the supported device protocol are SCSI-{1,2,3} and Wide - do all disks (like those recent above) supports @least one of them ? Or do I have to check the disks specs to see which protocol they support ? SCSI support is layered. Since the drives above support LVD (I think, double check that), then they should support Ultra Wide. As for special care: Make sure each drive is set to a different device number (Setting them as 1, 2, and 3 might be a good idea). This will be done by setting jumpers on the back of the drive. Also, make sure you get a good cable, crappy cables are the bane of SCSI. Finally, the SCSI bus needs to be terminated, on the internal side this is easy to do--just plug a drive into the last slot on the cable. -- \ |_ _|__ __|_ \ __| Jason Andresen jandrese@mitre.org |\/ | | | / _| Network and Distributed Systems Engineer _| _|___| _| _|_\___| Office: 703-883-7755 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message