Date: Tue, 10 Oct 2000 18:31:21 -0700 From: Leonard Chung <leonard@ssl.berkeley.edu> To: "Jeffrey J. Mountin" <jeff-ml@mountin.net>, Warner Losh <imp@village.org> Cc: kline@tao.thought.org, freebsd-stable@FreeBSD.ORG Subject: Re: Bad IDE Drive Message-ID: <4.3.2.7.2.20001010175336.02671740@yikes.com> In-Reply-To: <4.3.2.20001010190749.00c5cf00@207.227.119.2> References: <4.3.2.7.2.20001010124858.026637c0@yikes.com> <200010100509.XAA18135@harmony.village.org> <Your message of "Mon, 09 Oct 2000 19:06:31 PDT." <4.3.2.7.2.20001009190324.028c6d58@yikes.com> <4.3.2.7.2.20001009190324.028c6d58@yikes.com>
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Hi Jeff, Drive specs and current street cost aren't my primary sources. :-) Let me throw in a quick plug for a paper I wrote earlier this year which covered the whole issue of IDE vs. SCSI: http://www.research.microsoft.com/BARC/sequential_io It addresses most of the issues you raise here: RAID comparisons and actual empirical numbers. Of course, any measurements can only give an approximation of "real world" performance in a production environment, but the numbers are pretty compelling none-the-less. Also, as I've mentioned before, the mechanisms between two drives with similar RPM and capacity but different interfaces is almost always the same, so I'd be very surprised if longevity is an issue since they both have the same moving parts. Consider also that SCSI drives cost generally about significantly more expensive than a comparable IDE drive, so the difference in price/performance is huge. I started out being a bit of a SCSI guy, but I've become convinced of the soundness of the case for IDE. Many of the issues brought up on this list are similar concerns had myself when I first started looking into this whole idea of cheap storage (a <=$10K/terabyte). IDE has come a long way from the old PIO days where IDE and SCSI drives were made from different mechanisms and IDE meant cheap and unreliable. Things have changed these past few years with the advent of DMA and the sharing of drive mechanisms across SCSI and IDE product lines. Hopefully after reading the paper, it will hopefully make you reason to not chose those years older SCSI drives over today's new IDE drives. A quick disclaimer: This was a study done for Microsoft Research on Windows 2000, not FreeBSD, but it is reflective of the performance you can get out of the drives themselves. The unbuffered IO (i.e. straight to disk) numbers are probably the ones you care most about. Leonard At 05:45 PM 10/10/2000, Jeffrey J. Mountin wrote: >This smells like a techie sales pitch. Little meaningful info regardless >of terms and large words. Did I mention I'm a hard sell? > >You would need follow up with figures that involve more than one >transaction. Many more. The hardware may be similar, but the interface >is where the "real world" difference will be evident in a busy production >environment. > >The vagaries referring to price I must presume are talking about RAID >arrays (otherwise it's non-scenical). Seeing a comparison between the >same array with IDE vs SCSI would be interesting. Drives should have very >similar numbers using your comparison. > >With IDE I think most would agree that initial cost will be >lower. However, longevity counts, so total cost for the lifecycle should >be considered. The longer the period, the more likely that IDE will end >up costing more. > >Going strictly by drive specs and current street cost isn't near enough to >sell me, and surely others, on your ideas. Don't take offense either, >there just seem to be a few holes that need to be fixed. Even if you are >referring to a workstation or single user application where I have opted >for older "slower" SCSI drives than years newer IDE drives for performance >reasons. > >Anxiously awaiting the test results... 8-) > > >Jeff Mountin - jeff@mountin.net >Systems/Network Administrator >FreeBSD - the power to serve -- Leonard Chung - <leonard@ssl.berkeley.edu> SETI@home - The Search for Extraterrestrial Intelligence @ home http://www.setiathome.ssl.berkeley.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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