Date: Sat, 2 Dec 1995 14:40:49 -0700 (MST) From: Don Yuniskis <dgy@rtd.com> To: smp@csn.net (Steve Passe) Cc: freebsd-hackers@freefall.FreeBSD.org (FreeBSD hackers) Subject: Re: No Thumbs??? (lack of concensus) Message-ID: <199512022140.OAA13833@seagull.rtd.com> In-Reply-To: <199512021713.KAA04430@clem.systemsix.com> from "Steve Passe" at Dec 2, 95 10:13:36 am
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> Hi, Diddo. > >single *half* height or single *full* height? > > single, specifically I like the JDR Microdevices's ED-150 for 3.5" apps. It I assume "single *half* height"? :> > is well made mechanically, all metal except for the faceplate. The fan Ditto. Though the "knockout" is a full height -- I'll have to see if they have half-height blanks (or third height) available... > in this box is crap, unfortunately. > > >> used for things like tape drives). In its place I put a foam filter to > catch > >> dust. This allows airflow directly across the top of the drive. I also > > > >Hmmm... that's a good idea (tho' not quite as visually appealing! :>) > > Actually it looks like factory made if you take your time. With the above > mentioned box I remove the top-third faceplate blockout and cut a piece of "third"? is this a full height case with three third-height knockouts? > open-cell black foam slightly larger, which pops right in place from the back. > Looks like what nature intended from the front. I'll have to see if I can get half or third height knockouts with vent holes (the full height panel only has one set of holes along the *bottom* (tho' I could flip it over...) > >> get a GOOD fan from someplace like Digikey. Panasonic makes a line of > >> ball-beaing fans with much higher rated air-flows that the ones typically > >> found in disk cabinents. The oem fans also usually die in short order, > which > > > >And *another* good idea! I'll have to examine the fans on these cabinets > >a bit more closely... > > I don't recall ever seeing a quality fan in such boxes. The specs on the > panasonic fan I usually use: > > ball-bearing, 2.40 watts, 6.7 cfm, 32.0 db-A (digikey part# P9703-ND) Hmmm... the fan in this box is 25x80mm. Claims to be 250mA (i.e. 3W). Just gauging from size, similar fans (ball or sleeve bearing) in DigiKey catalog seem to be 25 - 40 CFM. Of course, it's thermostatically controlled so I'll have to hot-wire that... > >I was looking to put *two* 3243's in a fullheight external enclosure. > >Or, a single 1991. But, same problems (I imagine) would plague each... > > I recommend 2 3243's in 2 half-height boxes. They stack in about the same > space > as a double height box and give you alot more flexibility. Put a root > partition on both, you get some crash recover benefits. You also can do some > load balancing and get better scsi thruput. Get a couple scsi-I ribbon cable So far, my only disagreement is 2 drives in a *single* full height enclosure. :-/ > connectors and build a 3" connector to attach the 2 boxes, no bulky 3 foot > cable dangling between the two. One thing to consider, I have seen > combinations > of external boxes that became unhappy with mixed flat and round cables. Yes, I've seen/heard similar horror stories. > Something to do with impedance mis-match. Remember that each box has approx. > 8-12" of flat cable inside, so if you string together 3 or 4 boxes with > round cables there are a lot of impedance changes happening. I like to build > flat cables to connect all the boxes in a chain, including the link between > computer and 1st box. Ah, well, I'll hopefully buy good enough cables ;-) > >your intended application? :> Maybe just put a warning light and then > >hardwire a circuit to (unceremoniously) remove power from the drive at > hi-temp. > > I have wondered about this. At what temperature is it better to clobber the > file system and spare the drive a few minutes more of over-temp condition? > I suspect most modern drives will shut down when they get TOO hot. The > problem > is a drive that runs borderline for long periods of time, degrading its > lifetime. I guess that reaching the warning (yellow) temp means orderly > shutdown, if red is reached while program is still running just cut the power. Right. My point was that if the yellow is ignored, don't count on someone "observing" (i.e. reacting to) the red, either! I feel that yellow (to use your example) should only occur when things are becoming exceptional (i.e. you shouldn't be running yellow all the time!). Expect someone to fix the problem that is causing the yellow. If they don't and "red" happens, just go to a brute force solution. This can all be implemented with a few comparators, etc. > >How warm does the 3243 case get (use *top* side of finger to test). > > If you mean the cabinent it is in, top of finger, wrist, big toe, > it feels maybe 5 deg above room temp to me. If I can find an appropriate > thermometer around here I will get an actual measurement. > > If you mean the 3243 drive itself, I don't know offhand, not eager to open up > a cabinent to find out right now... Well, actually, *that's* what I was looking for... :-) How long has this been in service and what kind of (ab)use does it see? I'd like to order 4 of them next week (or comparable).
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