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RAID for Zero-G?
Cujo asks: "In all seriousness, I need a RAID that supports at least level 3 and stores > 500 GB, and I need to it work in zero-G (but not in a vacuum), and be able to take a fair bit of vibration and noise when turned off. I don't want to spend huge sums: I'm thinking well less than $50,000. I've looked at Apple's XServe/XRaid products, and they look great (about $10,000), but are they rugged enough and who is their competition? Some people make hardened RAIDs for military use, but I'm unfamiliar with the best candidates in that field (and do I really need mil spec?)."
How do you plan on getting this equipment into a zero-g enviornment? That will problable determine if you need hardened/milspec type equipment. If its going up on the shuttle, with those G forces on it during launch, then yeah, you probably do need 'milspec'. If its going to reside in a plane, that does zero-g free-fall testing, you can probably get away with something less... YMMV.
"The natural progress of things is for liberty to yield and government to gain ground." - Thomas Jefferson
They do use ThinkPads on the shuttle/ISS after all, so they must have the drives capable of this kind of thing. RAID cabinets and controllers have no moving parts (or maybe a fan or two), so I doubt they would be affected by zero G anyway.
UNIX? They're not even circumcised! Savages!
Hey just because NASA has a tight budget doesn't mean you guys can use Slashdot for your R&D!!!
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Love conquers all... except CANCER
Remember that a lot of mac kit is specifically designed to use convection to move air and therefore heat through the box. For example an old-style iMac will probably melt as it relies heat rising. Not something that is gonna happen in zero-g. You might need to be changing the fans and such like.
China has announced it intends to accelerate its Mars program, using experience and expertise from its fledgling lunar program.
They didn't mention China's use of highly reputable sources of expertise, such as Ask Slashdot!
How are you going to keep them down on the farm once they've seen Karl Hungus?
The heat is a concern, and the lower the power dissipation, the better.
The RAID performance in orbit doesn't need to be top drawer, but when it returns to Earth, I want it to perform well and not be a hassle to administer or set up, since there's a lot of data to analyze.
Helium balloons want to be free.
- Heat
- Air pressure
- Radiation
Testing tip:Convection cooling gets assumed into almost everything, so you'll have to make sure the gear gets some air forced over everything to keep it cool. Inside the hard drives, you've got those nice platters pushing the air for you, so that should be ok.
You indicate that there will be air, but not the pressure. You should test your system at the operating atmosphere and pressure for an extended amount of time. This is critical because the hard drives typically float on a cushion of the ambient atmosphere.
Since you're outside the 50 or so miles of air which filters out most of the radation common in space, make sure you have hardware ECC RAM, etc. It would also be good to make sure there is a hardware watchdog in place to protect the OS from hanging do to an induced CPU error.
I'd suggest you test the unit, then run the same test with the unit operating upside down, and on each of it's other 4 faces, as a minimum.
You've got an interesting project, good luck!
--Mike--
I have worked with these guys before and they are a great group. They have a lot of experience building rugged mass-storage solutions for airborne and military applications. In addition, they are a relatively small company, with a lot of engineering capability, so they should be able to give you personal attention and help you work through the various issues involved in this type of system.
You are sending up an experiment on shuttle mid-deck which I would hope implies that the experiment is worth the significant risk to human life and great expense that this requires.
But no, you are looking to cheap-out on the drives that are undoubtedly critical to the success of the experiment. That's pretty damn penny wise and pound foolish.
Having vented...
I suspect that NASA has specs and requirements for experiments on spacecraft if not for protecting the integrity of the experiments then at least to protect the astronauts and shuttle. What do those specs dictate?
If you can use COTS hardware then I suspect that laptop drives are your best bet for not only ruggedness but also weight, power draw, and size.
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"You are not remembered for doing what is expected of you." - Atul Chitnis
I guess he needs it for something simpler - such as skydiving
I know that whenever I skydive, I strap on my parachute, a reserve, and a 500GB raid pack. Makes the free-fall go just a little bit faster.
Some issues I haven't seen mentioned:
1) In zero-g, will lubricants (minimal as they are) be more prone to leak out?
2) In zero-g, will friction be slightly lower, and will this cause any problems? Does modulation of RPMs depend in any way on any component of friction that is influenced by gravity? How about head movement?
3) Is head movement and position affected by gravity? I'm guessing not, but then, I'm just joe random slashdotter.
4) Will vibration issues be introduced by the removal of the (possibly dampening) force of gravity? Note I am not talking about external vibrations here, I'm talking about vibrations of the hard drive itself.