Slashdot Mirror
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!!!
__________
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--
Please, for the love of God and all that is good, do not use an Apple product. We'll never hear the end of it.
compact flash memory is not very expansive (~200$ for 1GB retail)
it is pin to pin compatible with IDE so you can build a standard linux raid
if you buy bulk I think it will be in your price range
As of Postgres v6.2, time travel is no longer supported.
Boy, those budget cuts at NASA must be getting bad if they're coming to us for advice!
"Lawyers are for sucks."
- Doug McKenzie
For anything operating on the shuttle, you're gonna have to consider heat dissipation (convection cooling won't work!), outgassing properties (closed environment), vibration and mounting (not so much how the drives are affected, but how the drives affect everything around them), and gyroscopic forces, (There may be real issues with mounting a rack of 10k drives with all spindles on the same axis), size, weight, and power consumption, just for a start. You really need to provide a more complete spec to get recommendation,
What's your experiment budget? If you have the option of going solid-state (i.e. flash), that may simplify things - you mentioned write performance was not critical. You clearly want to use the largest, slowest (rotationally) disks possible to minimize space and power consumption. Perhaps a hardware ATA or SATA raid controller in a chassis with e.g. 8 180-250gig drives in a 0+1 configuration?
-Isaac
I am not a lawyer, and this is not legal advice. For Entertainment Purposes Only.
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.
I've heard it costs about US$10K per pound to put an object into orbit.
If that's true, why isn't weight more of a consideration?
I presume your project's individual cost limit is preventing you from investigating solid state disk solutions, which would probably be less susceptible to shock than platters in a magnetic disk hard drive.
"Provided by the management for your protection."
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.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
Which brings up a few other questions besides technical limits of hard drives in space...
On airplanes they want electronics shut off during takeoff and landing. I would expect NASA to be no less stringent about 'spurious radiation' during takeoff and reentry, though probably more technical and perhaps more flexible if you shield carefully.
I also wonder what they think about 'little embedded gyroscopes' (hard drives) on the shuttle. Do they have to know about every one so they can account for it, are they just negligible, are they cumulative, or can you mount every other drive in the rack upside-down to cancel out righ-hand-rule effects?
There used to be a "Space Shuttle Operators Manual" for publicity/potential customers. I believe the local library has one, so I should check out the 'electronics restrictions' section.
The living have better things to do than to continue hating the dead.
Maybe not to the drives but the whole system must be considered. Drives don't work well when the power or data cables shake off or the raid board or CPU on the system comes loose. Machines exist to shake 'n' bake equipment (NASA or its contractors will have them). I wouldn't send up an experiment unless it passes a ground simulation of the vibration, G-loads, temperature, etc. that it will experience on liftoff, reentry and orbit.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
If you want RAID-3 you pretty much have to go SCSI. There may be a way to do it with ATA drives, but I haven't heard of it.
The other reason you want SCSI is reliability. That's one of the reasons SCSI drives are so much more expensive. I've seen more than one SCSI drive get dropped on a hard tile floor and still be usable for a year or more (These are half hieght Seagate and IBM, 7200 or 10k RPM, YMMV).
If you do decide to go IDE, try to use laptop drives. They have MUCH better g-force tolerance than the standard 3.5 inch IDE drives. However, I've still never seen one survive getting dropped on a hard tile floor. Shock and vibration are different things, though, so the laptop drives still may be a better choice. You can
You could go flash, and that would take care of the vibration/shock issue, but at 1GB each that's an assload of IDE controllers you have to somehow get working together. Assuming 4 per controller, that's still 125 controllers. Even if you solved the IRQ problem, where would you put all of them? Space is a precious comodity on these missions. Plus at $200 each that means $100k for 500GB, which seems to be out of your budget range. A custom motherboard with 125 PCI slots is certainly out of your budget range.
What I would do is talk to standard RAID vendors like EMC^2 or Ciprico and see what they've got. I know a company that would be happy to design and build a shock-mount for a standard raid chassis for you for probably under $10k. You could also go somewhere like Musicians friend and buy a road case, which will certainly have some anti-shock measures, for a few hundred dollars if your needs won't be too severe.
I very much doubt that zero-g will be an issue at all. The things that will be problems have already been mentioned by other posts.
Under capitalism man exploits man. Under communism it's the other way around.
I don't think hard drives are vacuum sealed. Most of the hard drives I have taken apart have an airhole. I have been told it is for pressure equalization. Some of the old IBM Deskstars have a warning to not cover the hole. So at the very least I would not assume that a hard drive is sealed.
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.
They cannot have a vacuum in them, as the head gap is created by the bernoulli effect, and without it, the drive would quickly destroy itself!
Nothing to see here; Move along.
yea ... go with one of those xserves. that'll be like $10k. then, pay me the other $40k and i'll hold it for you
vodka, straight up, thank you!
The Xraid would likely be tought enough, but sadly, the Xserve itself my not be able to handle launch. It's so thin, that many users have bent the tope covers, or had the entire unit warp on them.
Cooling the units shouldn't be an issue, the fans are powerful enough that in null gravity they'd be able to propel the unit:)
And, i know that at least one company was planning on using G4's in space, so there should be some studies on radiation effects and such on those processors floating around somewhere....
I wanna see some goofball jump out of a plane with 1/2 TB of NetApp strapped to his back :-).
With that kind of weight, they would have to do RAID1 of the skydiver as well.
I like music
Comment removed based on user account deletion