Date: Fri, 23 Nov 2001 17:59:12 +0100 From: Robert Suetterlin <robert@mpe.mpg.de> To: Ted Mittelstaedt <tedm@toybox.placo.com> Cc: freebsd-questions@freebsd.org Subject: Re: why are You asking here Message-ID: <20011123175912.B1170@robert2.mpe-garching.mpg.de> In-Reply-To: <008401c17410$83770a40$1401a8c0@tedm.placo.com>; from tedm@toybox.placo.com on Fri, Nov 23, 2001 at 03:18:01AM -0800 References: <20011123112138.A6496@robert2.mpe-garching.mpg.de> <008401c17410$83770a40$1401a8c0@tedm.placo.com>
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Hi > Hi Robert I hope you don't mind me cc'ing the list. ok, perhaps someone likes to read it. > Well, asking FreeBSD to solve a problem that Sun can't solve is a bit > surprising, > you must have a lot of faith in us. Yes I do. And then there is net- and openbsd, I just referred to FreeBSD because this is my flavor. > Um - there ARE Sparc laptops so I think they have dealt with this already. Well. Yes. There are, and one (ten year old) model is just now flying in our current space experiment. > But in any case, I'll make a few points here: > > 1) The power consumption and all that, while it's important, is not > something that FreeBSD can solve for you. This is purely a hardware > issue. Now, if you have some hardware already in mind that you think > can do it and your just looking for an OS to run it - well that's > something else, tell us what it is. If not - well I think your first > stop is the hardware mailing lists. Yes. No. Perhaps. Good idea that You mentioned the hardware page... Still the hardwarepage is not the first stop if the application that solves my problem is bound to a specific operating system, which then turns out to be bound to some specific hardware. > 2) While you outlined the problem your looking at: [cut] > what struck me is that your not saying anything about weight limits. Make it as light as possible... and BTW, I gave the volume limit. > Well I'm not an expert here but it seems to me that it must cost hundreds, > perhaps thousands of dollars per pound to lift anything into orbit. millions. > That would seem to indicate that with the size of data storage your talking > about, that your primary concern should be getting the densest storage medium > possible, as even the most expensive and densest storage medium available today > no matter how expensive it is, is going to pale in cost to the money needed to lift > it up to the ISS. You must not forget the total project cost, of course, and that there is a complicated budget which allows for different costs in seperate areas. So for example we cannot spend all of our hardware money on the storage, but must also spend some on the experiment itself. And we cannot spend all the transportation budget on launching a onetime solution, we must also plan for transporting defect parts, spare parts and data! The main problem with the ISS is, that there is no Broadband Connection to get the data back to ground. So we must store the data in a form that can be easily transportet. > I am not at all convinced that tape storage is any kind of answer for > you. Besides the fragility of the medium, there's the fragility of the > recording mechanism itself. All tape drives, being mechanical things, > will wear and drift out of alignment. I simply cannot imagine any kind > of data tape drive manufactured today lasting for 5-10 years with any > reasonable amount of use, [...] 1) Well why tape storage? Did I indicate tapes in my mail? Sorry for beeing so specific, I do not want to specify 'tapes' already. 2) Our datacenter is using tapes for data storage and so far (under very heavy use over a very long time) everything is still working. Of course we must plan for wear of the machinery. And we must have a solution that can be serviced by astronauts / kosmonauts easily. > [...] and a considerable amount of weight and space > will be consumed by the cartrige, mechanism, etc. [...] We have a second locker that can hold full / spare media, that is the same size as the data recording facility. > [...] Wouldn't you really > be needing to look at something completely solid state here? I mean, > there's flash cards that sell on the street that will hold a gigabyte, > surely someone could custom-build something for you that would hold a > lot more than this. 1) Flash cards are much slower than tape storage. Static Memory is really expensive. I cannot see any multi-Terrabyte Solid State Storage on the common market today. 2) Before we can use a storage system on the ISS we must test it on the ground for some time. I would like to use a more toolbox like design, that allows to change separate parts of the hardware and the software gradually while newer versions appear on the market. Still, how the system works in general is not allowed to change too much over time, as this will prevent solid testing. The Budgeting for (space)experiments also encourages evolutionary change in experiment setup and supply, because You get some part of Your budget every year and not all at once in the beginning. > 3) What exactly is a HSM going to do for you? HSM is useful if You have a hirarchy of storage with different qualities. So it will help in any application where You apply several storage solutions that have differnt qualities --- i.e. density, price, robustness, mobility, bandwidth, etc. --- to specific problems. Like Ram, Flash Memory, Static Memory, Harddrives, Tapes, DVDs, what do I know. Our experiment should run 24/7 if it would be possible. But at the least it should be possible to run it continously for 45 Minutes at peak data rates. The total experiment time is estimated to at least 3 hours per week. This means aprox. 150TB of data per year. If there is a shuttle mission each month, they will have to transport 10TB of data each time. Speaking in GByte Flashcards that is $5.000.000 in Flashmemory every two months. Ok we could recycle some of that memory... And Flashmemory will also get severe problems with hard radiation. Redundancy will increase price by aprox. 30%. So we talk about $6.5M If we will get larger data volumes in the future (because experimentalists always want higher data rates and longer experiment time) then prices will scale accordingly. Speaking of a Solid State Solution. First I cannot guess easily the price of 10TB Static Ram. Second, if You compare the size of a Ram Chip to a 100GByte Tape, I would say overall datadensity is similar. Of course You can get Memory much denser if You remove Packaging but not by an order of magnitude. Of course using a solid state storage to store for example 45 minutes of data could be very reasonable. Harddrives are a problem, because they disturb microgravity. As will all rotating objects, because of the enormous torque they can generate. So what can an HSM do for us? I guess it depends on the capabilities of the HSM. I believe, that our system will need a hirarchy of storage systems, specialised in specific tasks. I also would like to use the same general technique today that we will launch in five years (and then use for up to ten more). So I would like to use standard hardware and software solutions. These will most likely adept to the future automatically. An HSM would be an important building block in my concept of a solution to the data storage problem, as it relieves me of all the problems connected with hirarchical storage management. This does of course not prove that I need HSM at all. I might have a complete misconception of how to handle this amount of data at all. Sincerely, Robert. -- Robert Suetterlin (robert@mpe.mpg.de) phone: (+49)89 / 30000-3546 fax: (+49)89 / 30000-3950 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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