Date: Thu, 27 May 1999 23:13:46 -0400 (EDT) From: Jay Kuri <jay@oneway.com> To: jin@george.lbl.gov Cc: chuckr@picnic.mat.net, richard@pegasus.com, hardware@FreeBSD.ORG Subject: Re: Support for Symbios vs. Adaptect SCSI Message-ID: <Pine.BSF.4.05.9905272251060.11441-100000@daedal.oneway.com> In-Reply-To: <199905280215.TAA07899@george.lbl.gov>
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Hello, I realize this is a technical merit discussion... but wanted to put my $0.02 in... I've been building servers using both adaptec and symbios cards for quite some time. About 2 years ago I stopped using adaptec cards in favor of the symbios-based cards. For the most part, up to that point I was a die-hard 'nothing but adaptec in my machines' guy. What started it all was that I started having difficulties with adaptec cards flaking out. They would just spontaneously not working... causing scsi errors... etc. Mostly on the 100Mhz motherboards. So I reluctantly decided to try the symbios cards. They worked 100% fine in all of my problem systems. I noticed no performance impact in those machines at all. Since then, I've been using symbios cards on almost all of my servers. Admittedly I have not run benchmarks on the different systems that I have running, but I can't tell any difference between my adaptec-systems' and my symbios systems' performance. I've got a large raid-array hanging off of a symbios differential-scsi card and have no complaints. The performance difference (that I can't see) with the adaptec cards is not worth 3+ times the price of the symbios cards. For me, when scsi-performance starts becoming a bottleneck, I find I'm usually switching to a DPT SmartRAID/CACHE controller anyway. My $0.02, Jay > > Trouble is, your report has no specifics as to what is faster or better, > > and even you don't recall where it's from, so it's of nearly no more use > > than rumors. I'm not trying to be offensive, but (unless you have some > > reason to assign more importance to your statement, that you haven't > > passed on to us), this kind of stuff is misleading to folks. > > > > Those "test reports" could very easily have come from biased > > benchmarking, something we're all familiar with. The fact that NCR > > chips show up in many interfaces, well, they ARE cheaper, aren't they? > > You have to have at least some kind of detail in reports such as yours, > > to make the data believeable. > > The SCSI benchmark is very depended on the controller and drive combination. > SCSI hard drive 1 may have #A throuthput on Adaptec controller, and #B > throuthput on Symbios controller, but the SCSI drive 2 could have #B > throuthput on Adaptec controller, and #A throuthput on Symbios controller. > > Unless someone tested a bounch of drive under both Adaptec and Symbios > SCSi controllers, your never can tell the truth. One reason is that the > disk dirve manufactories can make very different arbitrition timing as we > found. Even you chained different SCSI drive on the same controller, you > may end up having a serious trouble to make high SCSI bus utilization. > > Adaptec SCSI controller was very sensitive to the terminator and cable > length a few years ago, so we stopped using it. We used Symbios instead. > Since I have no curent Adaptec SCSI controller, I cannot tell how good it > is. I only can tell we are happy with Symbios chips. We can get bits going > almost saturating the SCSI bus at 85-92% utilization. I am very eager to hear > if someone can tell us how Adaptec controller can do, so we may get one for > benchmarking. > > So, at this point, unless you have done some intensive-combined SCSI > benchmark, no one shall tell who is better. If you can get SCSI bus > saturated, you are there. > > Another thing is the price/throughput ratio. In a low performance chain, > you could chain up to 15 disks on a SCSI-3 controller. The bus is always > saturated when all disks try to talk. The best throughput is 40MB. > In a high performance chain, two high speed SCSI-3 drives can almost > saturate a SCSI-3 UW controller. Now you need at least 7 controllers > or 15 dsks; then the price is the big issue. The 2% differnt performence > between different SCSI controllers can be ignored. > In talking 1TB disk sub-system, I would not worry about the 2% or even 5% > (could be seen at most) differnce of throughput for different SCSI controller. > The price is more important. > > Just a coule of cents. > > -Jin > > at this point. > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hardware" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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