Date: Fri, 20 Jun 1997 02:29:50 -0700 From: David Greenman <dg@root.com> To: Simon Shapiro <Shimon@i-Connect.Net> Cc: "Justin T. Gibbs" <gibbs@plutotech.com>, FREEBSD-HACKERS <FreeBSD-hackers@FreeBSD.ORG>, FREEBSD-SCSI <FreeBSD-SCSI@FreeBSD.ORG>, Brian Tao <taob@nbc.netcom.ca> Subject: Re: Announcement: New DPT RAID Controller Driver Available Message-ID: <199706200929.CAA12213@implode.root.com> In-Reply-To: Your message of "Fri, 20 Jun 1997 01:39:04 PDT." <XFMail.970620013904.Shimon@i-Connect.Net>
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> >Hi "Justin T. Gibbs"; On 20-Jun-97 you wrote: >> >An excellent mechanical engineer designed a wonderful metal system (both >> >canisters and carriers). We had up to 30% perofrmance loss on random >> >seeks with system. It baffled anyone until another engineer decided to >> >test the drives on his desk, outside the box, outside the carriers - >> >Yes, the performance was back. Turns out soft errors were masked and >> >the rigid but ringing-resonating nature of steel and the high packing >> >density caused drives to resonate the cabinets and cause miseeks. >> >> Pluto's drive sled design uses a very simple and cheap suspension design >> to deal with this very problem. > >Proof that this problem is not unique. There are several ways of dealing >with it. Worse was hanging devices on... springs! Before everyone throws out their metal drive enclosures in favor of plastic ones, let me say something about my experiance. Wcarchive used to lose a couple of drives a month back when they were housed in plastic enclosures. I noticed that the drives in that box ran hot, and I finally got tired of flying down to the Bay area so often to deal with it and convinced WC to replace the cabinet/enclosures with an all-steel one made by Kingston. This was about a year ago. Result: The drives run almost cold now and we haven't had a single failure in that array since. All of our drives have fairly well balanced spindles and don't vibrate all that much, and I've never seen a reported seek failure or noticed any slowness. In my opinion, the all- metal enclosure is a significant factor in the cooling of the drives and these days I wouldn't consider anything else. YMMV. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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