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Supercomputing Hardware

Three-Mile-High Supercomputer Poses Unique Challenges 80

Nerval's Lobster writes "Building and operating a supercomputer at more than three miles above sea level poses some unique problems, the designers of the recently installed Atacama Large Millimeter/submillimeter Array (ALMA) Correlator discovered. The ALMA computer serves as the brains behind the ALMA astronomical telescope, a partnership between Europe, North American, and South American agencies. It's the largest such project in existence. Based high in the Andes mountains in northern Chile, the telescope includes an array of 66 dish-shaped antennas in two groups. The telescope correlator's 134 million processors continually combine and compare faint celestial signals received by the antennas in the ALMA array, which are separated by up to 16 kilometers, enabling the antennas to work together as a single, enormous telescope, according to Space Daily. The extreme high altitude makes it nearly impossible to maintain on-site support staff for significant lengths of time, with ALMA reporting that human intervention will be kept to an absolute minimum. Data acquired via the array is archived at a lower-altitude support site. The altitude also limited the construction crew's ability to actually build the thing, requiring 20 weeks of human effort just to unpack and install it."
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Three-Mile-High Supercomputer Poses Unique Challenges

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  • Simple answer: Have redundancy all over the place so it doesn't matter if a few modules fail. The repair crew can go in once a year and swap them.

    • Re:Redundancy! (Score:4, Insightful)

      by Synerg1y ( 2169962 ) on Friday January 04, 2013 @01:30PM (#42477109)
      I don't think the article mentioned redundancy either day... but consider what they did: they took pre-manufactured components, hauled them up 15,000 feet and installed them... not set them up. I'm sure somewhere in this process short of hiring ALL first year grads they most likely introduced typical datacenter redundancies... load balancing, failover, arrays, etc...

      The article is about the challenges posed with operating the components at such a high altitude and for people who aren't used to high altitudes, they really can't work effectively up there limiting the pool of tech support personnel you can send up there significantly.
    • The only IT related things from the actual article are:

      Use SSDs.
      Use bigger fans.

      Seems kind of a waste to not put that in the blathering summary.

    • Or if they're having trouble finding a sysadmin, I'm available. My Spanish is decent and I have extensive experience in avoiding physical activity thus reducing the need for oxygen. Email address above!

  • Drove three of my friends over Tioga Pass in the Sierra Nevada's in the north of Yosemite...couple of them had never been out of Louisiana...between 8000 and the summit of the pass at ~10,000 ft meant me driving while everyone else suffered from altitude sickness...the only cure is to remove to a lower elevation. Having grown up in the sierras, i was used to the elevation...but if you're not acclimated, then you're going to walk 20 feet and have to sit down to rest for 10 minutes.
    • Mauna Loa is about 13,000ft above sea level at the peak. I was the only one that didn't have a problem breathing, but our rental SUV barely made it up... it was choking on the thin oxygen most of the last quarter of the way up. Might be one of the reasons we weren't supposed to go up the mountain according to our rental agreement.

      • It's the fuel/air *mixture*. As you go up in altitude, you're getting a lesser volume of air, but the same amount of fuel. Modern injection systems do a better job of adjusting for air pressure, but your engine still needs to be tuned for the altitude it's going to run at. I used to live in Reno (4500 ft) and every time I drove down to San Fransisco (sea level, obviously), my car would run like crap. In town, I'd always see California cars belching smoke from all the unburned fuel in the exhaust.
        • by tibit ( 1762298 ) on Friday January 04, 2013 @02:10PM (#42477711)

          I think you misunderstand how it really works.

          Modern cars have air mass sensors -- they sense exactly how much air is coming into the engine, no matter what the pressure of the air is. This control is instantaneous, there's no adjustment period. The amount of fuel injected into the air is based only one the air mass and some slowly adapted tuning constants. The "lesser volume of air, same amount of fuel" assertion is completely untrue!

          So, you may ask, what if the relative partial pressure of oxygen in the air dropped with altitude -- that would be a problem, as the car only senses the air mass, not oxygen mass. It has to adapt the fuel amount relative to amount of air only based on the readings from the exaust oxygen sensor. This is not instantaneous -- the oxygen sensor readings are in effect low-pass filtered and affect the air-fuel mix very slowly, with time constants, I'd guess, on the order of an hour. Here's the good news: the relative partial pressure of oxygen stays pretty much constant at altitudes where there are roads. So it's not a problem.

          Your car has a problem of some sort, what you describe is not normal behavior.

          I was driving in a turbocharged car in the Alps and there were no performance problems related to altitude changes -- the absolute boost pressure was maintained by the ECU per throttle commands and load factor, as desired, delivering apparently same mass of air to the engine, at given load, as at sea level. This worked even on some of the highest paved roads out there. Even if there was no compressor in the intake, the engine would simply lose performance with altitude, but recover it without any undue effects when driving down.

          • Who says he rented something even remotely new to drive up the mountain?
          • by Anonymous Coward

            Can you describe this with a car analogy?

          • Stochiometric.

            Fifteen years and I finally have a use for remembering that term. =D
          • Forced induction engines perform alot better in high altitudes due to them actively cramming air into the engine. The fact that your turbocharged vehicle did alot better in the Alps compared to his N/A SUV is no surprise.
      • I, an out of shape old man, was able to walk around Mauna Kea (13,700 ft) without much problem as long as you move slow. 16K feet would probably put me on my ass. FYI: While visiting the area, go up Mauna Kea in the day and at night. The landscape with all the observatories is mind blowing in the sun and at night.
        • by tibit ( 1762298 )

          Agreed. That's the key: you have to find a slow, steady pace. Going too fast makes for a very crappy day.

      • Lucky you didn't get fined by your rental car company - there are reasons those provisions are in the agreement and I believe most of the modern cars have GPS units on them. We took a tour up there about 6 years ago, going on a specially modified bus that had no problem hitting the summit (I'm also surprised they let a rental car up the final road as they limit the traffic up there to keep the dust level down which can impact the observations - I thought you had to have a sticker/permit to go up to the top
        • This was a about 10 years ago, I don't recall needing any special sticker/permit to gain access to the road, but that could have been handled by the driver while we were at a lower altitude (we stopped at a base station of some sort). This was probably before they started adding GPS units to most rental cars. I wouldn't be surprised if that practice is less common in Hawaii anyway as there are relatively few places to take a stolen car. While our rental was sputtering along, we did encounter other smaller c

      • I am going to assume that was Mauna Kea [] and not Mauna Loa []. There is a road to the summit of the former, paved part of the way, for the people who work at the observatories up there. There is a 4WD unpaved "road" part way up the slope of Mauna Loa but no vehicular access to the summit.

        Rental car companies don't like having to come collect their vehicles from Mauna Kea after people have destroyed the brakes in them riding them all the way down the hill (or having negative interactions with invisible cows [] at

      • by ncc74656 ( 45571 ) *

        Mauna Loa is about 13,000ft above sea level at the peak. I was the only one that didn't have a problem breathing, but our rental SUV barely made it up...

        How many decades ago was that? Anything reasonably modern (and rentals are usually no more than a year or so old) would be fuel-injected and computer-controlled; altitude shouldn't affect it like that. I've driven up to Pikes Peak (about 14100', IIRC), and my car didn't have any issues. (It was a 2004 Oldsmobile Alero...nothing particularly exotic. Still drive it to work every day.)

    • Re: (Score:3, Informative)

      by Anonymous Coward

      ...the only cure is to remove to a lower elevation.

      Top Gear suggests viagra

    • No offense, but those friends of yours are wimps. I live in Georgia, am 59 years old, smoke cigarettes and do not exercise regularly. OTOH, I'm also not obese...However, each year for the last 3 years, my son and I have traveled to Sequoia/Kings Canyon National Park (one of the best I've ever seen, BTW) for a weeklong bout of trail hiking. Most of the trailheads are in the 7-8K ft range, with many of the trails reaching 10,000 ft and more. Certainly, we were both pausing more frequently as the elevation ros
      • you didn't drive from sea level to 10,000 feet in about four hours...that's rather a bit fast to be ascending that'll getcha if you do...i promise
        • by fotbr ( 855184 )

          Taking off in an unpressurized small plane and flying up to that altitude (granted, starting at about 400ft) in a lot less time than 4 hours (we took about 15 minutes) didn't "get" me or the other two folks I was flying with. Then again, we didn't get out and go for a walk at that altitude either.

  • say what? (Score:2, Insightful)

    by Anonymous Coward

    134 million processors, 140 kilowatts?!?

    1 miliwat per processor?

    • The processors are custom made processing boards.. they are not CPU's you would get off the shelf. They are made to do only one task.

  • The article mentions how hard-disks fail at this altitude because the heads can't glide over the platters on a layer of air because it's too thin. The thin air also is less effective for cooling. However, it didn't say if there's been any consideration of an increased incidence of high-energy particles from outer space causing random faults even in solid-state components.

    • by tibit ( 1762298 )

      The hard drives don't belong at that altitude, then. The correlators can well be completely diskless machines, even without a solid state drive. They can boot over the network from the lower-altitude server station.

    • by ls671 ( 1122017 )

      This is ridiculous. Just pressurize the server room or whole building and be done with it. That layer of air would automagically reappear for the heads to glide over the platters.

      As for particles, I know nothing about the subject but I guess that mountain isn't much closer than we are from the particle sources. I do not think the additional layer of atmosphere said particles have to go through to get to us makes a difference.

      My understanding is that particles are deviated at higher altitude than mountains b

      • This is ridiculous. Just pressurize the server room or whole building and be done with it. That layer of air would automagically reappear for the heads to glide over the platters.

        Of course that means that the room pressurization would be a single point of failure for every hard drive you had. Lose pressure and every drive suffers a head crash simultaneously... Oops.

        If I didn't need the storage volume I'd certainly prefer drives like SSDs that didn't require pressurization to work at that altitude. One le

  • Mis-interpreted the article title and though that someone was building a supercomputer that is three miles tall. I bet that poses unique challenges too.
  • by Anonymous Coward

    Any discussion in TFA about why they aren't just sending that data over optical cables to wherever would make sense to house a data-center? e.g. ground-level?

    Why does it need to be so near the array?

    Speed of signal over fibre can't be the difference (i.e. what difference does 1 km or 40km make? not much).

  • The far side of the Moon. No clouds, no rain, and only a little bit of dust every so often.
  • They are combining signals from dishes separated by up to 16km so it is not a necessity that the supercomputer be right next to one of the dishes. Why not build the supercomputer at the base of the mountain instead of the top. They are already beaming raw data around so it will not make a difference.

  • Just virtualize the supercomputer in the clouds and put the virtual machine on the mountain!


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