Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Hardware

Low-powerered Ethernet Hard Drive? 90

Posted by Cliff from the on-a-smaller-scale-than-NAS dept.
WotPeed asks: "The company I work for builds extremely sensitive electric and magnetic field sensors. The project I'm just starting needs to use a hard drive to store the digitized data for long-term measurements (no more than 20GB). Unfortunately the hard drive has to be external to the sensor because it generates too much magnetic interference (hard drive needs to be at least 20 feet away). I'm therefore building an ethernet link into the sensor so that it can connect to a remote hard drive. Wireless is an option for a later revision but we're going with wired ethernet at first to keep things simple. There are plenty of network attached storage devices out there but they all assume they will be used in an office environment, and therefore consume a LOT of power. I'm looking for an ethernet hard drive that consumes less than 10W (this system will be used outdoors and runs on 12V batteries). Does Slashdot have any suggestions before I roll my own? I don't need any of the fancy features found in most NAS solutions...I just want a hard drive I can FTP to."
This discussion has been archived. No new comments can be posted.

Low-powerered Ethernet Hard Drive? More

Low-powerered Ethernet Hard Drive?

Comments Filter:

  • IBM MicroDrives? (Score:3, Insightful)

    by Bastian ( 66383 ) on Sunday May 18, 2003 @07:04PM (#5988198)
    I imagine that MicroDrives consume very little power due to their small size and the fact that they can be powered by a PCMCIA slot.

    I'm sure the hard drives used in many MP3 players such as iPods also consume very little power. . .
    • The drives in iPods, et cetera, are normal, 2.5" laptop drives - which makes them cheap as well (since they're mass-produced)
      • Wrong. The drives in iPods are 1.5 inch drives. :)

      • Re:IBM MicroDrives? (Score:5, Interesting)

        by Gruturo ( 141223 ) * on Sunday May 18, 2003 @07:21PM (#5988298)
        Actually the Ipod uses a non-cheap, not-so-mass-produced 1.8" hard drive - that's why it's so small. Apart from this, yes, I fully agree.
        I recently replaced the hdd in my laptop with a 40GB one, which eats 2.2 Watt and cost me less than 100 Euro.

        How you're gonna hook it up a fastethernet without a PC in between is another story :-)
        (but I think such interfaces do exist).

        Another option could be a Firewire or USB2 enclosure - they allow fairly long cables - up to 20 metres (sorry no body parts used for measurements on this side of the pond) for firewire on sale at the 1394 store [1394store.com]. Linux and Windows have no problem using them.

        Just my 0.02

        • (sorry no body parts used for measurements on this side of the pond)

          Fine with me. I'd rather have 20m than 20 yards, anyway.
        • Another option could be a Firewire or USB2 enclosure - they allow fairly long cables - up to 20 metres (sorry no body parts used for measurements on this side of the pond)

          That would be 196.85 hands.

        • Actually the Ipod uses a non-cheap, not-so-mass-produced 1.8" hard drive

          ...

          How you're gonna hook it up a fastethernet without a PC in between is another story :-)

          I have an iPod myself and that was the first thing that came to mind. But, like you say, the "PC" inbetween is the rub.

          I thought Firewire and USB2 cables were much more limited in their maximum length. I'll look into that option some more. I don't relish the idea of building a Firewire interface into the sensor but I guess it's an option.

    • A microdrive or solid state disk are good options for the storage device, but there still needs to be an intelligent device to act as an interface between the ethernet line and the disk. That's what I'm having trouble finding.
  • How do you propose to do wireless without EM interference? Sound waves? Gravity waves?
    • How about this? [slashdot.org]
      • Well the darn thing doesn't work yet and like they said "they are working to have it more resistant to changes." From experience you don't want to wait for promised technology...it is rarely delivered on time.
    • Why with a waveguide of course ;~)

      (For those of you who don't know, a waveguide is basically a wire or metal box connecting two or more locations allowing EM waves to travel. One common example of a waveguide would be coax cable.)
      • Actually a waveguide is essentially a metal pipe - normally rectangular in cross section. The EM signal actually travels through the air *inside* the "pipe", and not through the metal casing, which just serves to guide the EM waves (hence waveguide). It's generally used for high frequency stuff in the multi-GHz spectrum where attenuation through transmission along a conductor copper becomes a problem. Coax cable, is just that; a cable with two conductors at different axial radii.
    • have the transmitter far enough.

      heck.. he could have a gsm on a 20feet serial cable transmitting all the data back to the office.

      i believe this would be a more standard way of handling such thing anyways, certainly cheaper and easier than finding a hd with networking interface and be low power at the same time(he would pretty much have to roll his own). it would also provide the information IN REAL TIME, so IF the machine would get damaged you would know instantly and not 6 months later that it didn't wor
    • How do you propose to do wireless without EM interference? Sound waves? Gravity waves?

      Our sensors work exclusively in the low frequency regime (0.01Hz-50kHz) so the RF interference from a transmitter isn't necessarily a killer. There will be some issues to overcome, for sure, which is why we're putting that part off until later.

      • >There will be some issues to overcome, for sure, which is why we're putting that part off until later.

        This is -exactly- why the first 90% of the development takes the first 90% of the time, and the remaining 10% of the development takes the remaining 90% of the time.
    • Considering that "The company (the poster) works for builds extremely sensitive electric and magnetic field sensors" it just may be possible that they are trying to measure gravity waves.

  • Roll Your Own (Score:5, Informative)

    by MBCook ( 132727 ) <foobarsoft@foobarsoft.com> on Sunday May 18, 2003 @07:23PM (#5988302) Homepage
    I'd think you'd have to roll your own. That said, it shouldn't be too hard to do. Just take a laptop drive, interface it to a microcontroller (search Google and you can find code and such to interface PICs, Amtels, HC11s, and others to HDs). Add ethernet (either a ethernet chip, you can find info on interfacing those with the same microcontrollers) or just use a reliable ISA card (3c509s are very well documented) and connect that to the microcontroller (also easy to do).
    • Yeah, that's basically my plan if I have to roll my own. I'll probably use a PC-104 CPU board with an ethernet and IDE interface already on it. I've found a couple of those that come in around 2-3 watts. That will suffice, but a lot of that power (well, some of it anyway) is wasted by things like VGA and USB interfaces that I'd rather just not have. Building a custom board starting from the controller is easy enough, but far more costly than buying something off the shelf.
      • parvus makes a five port 10/100 ethernet switch with extrended temp ratings in a PC/104 form factor (but you can use it for anything). It consumes just 1.25 watts. We had to hunt high and low to find a COTS switch for our own battery powered datalogger within this power budget. Most ethernet hubs/switches consume 3 to 5 watts.

  • Nowadays I'd recommend an external USB/FW HDD. Maximum cable length will be suffcient and power consumption should be reasonable - at least the models which use notebook HDDs. And you can watch the prices dropping...

  • You'll be rolling your own (Score:5, Informative)

    by n9hmg ( 548792 ) <n9hmg@@@hotmail...com> on Sunday May 18, 2003 @07:34PM (#5988353) Homepage
    The slowest Seagate 20GB drive i found consumes 24 watts. You'll still need an interface - cpu, memory, network...
    You're talking about NAS. So far, as you note, that's always been an office thing. They're made with ready power and heat dissipation taken for granted. I can't imagine a company with a real need for such a specialized requirement (as in, you're about the only case it's ever been needed) needing "ask /." help. If it's a power availability problem - spacecraft maybe?... you're not looking for a COTS solution... there would be none. If it's a power DENSITY problem... consolidate all the drive needs in a server away from the environment you're measuring.
    Incidentally, just so you don't embarrass yourself in front of your boss... wireless, at least in the most-commonly used sense, uses both electric and magnetic fields, most commonly at 2.4 or 5 GHz. Hell, conventional ethernet is something like DC-UHF, but mostly contained in the cable... perhaps something optical might be better-suited to your needs?
    Frankly, I think I'd take the DC outputs of the sensors and route them as the center conductors of good-quality coax, and bring them all to a bank of A/D converters somewhere away from the environment being measured.... can you give some kind of detail about the environment?

    Anyway, when you roll your own, you'll have to use something like a Hitachi microdrive. The 1GB drive consumes 8-1/4 watts on write. Maybe a transmeta-based motherboard won't break the rest of the budget.
    I'd be glad to work on it. I need a job.

    • Re:You'll be rolling your own (Score:4, Informative)

      by DancingSword ( 412552 ) on Sunday May 18, 2003 @08:35PM (#5988615) Homepage Journal

      Embedded Linux mag used to have micro ( smaller than mini-itx ) motherboard from ZFLinux.com [zflinux.com], but now they sell system-on-chip thingys, so maybe that'd be a bit too much hacking...

      here's one 2.7 inches by 1.6 inches [linuxdevices.com], it has an IDE interface and a 486sx...

      Ah HA! Gotcha!
      LinuxDevices.com:Top:Hardware:Boards:Single-board computers HERE [linuxdevices.com].

      Right, so that takes care-of the motherboard, so to use a flash-card or micro-drive, you need either anATA-to-CF adapter [acscontrol.com],
      or, if you need more than a pair of 2GB CF cards, maybe one of these flash-disks [adtron.com] ( ATA, SCSI, PC/104? that's what the ZF boards were called! ),
      or you can get an all-in-one IDE MicroFlash Card from MagicRam.com [magicram.com],
      or dig Dan's Data's review of the VME CF-IDE adapter [dansdata.com] ( neat that it can run as either ATA-master OR ATA-slave, unlike the competition, so you could get 4GB of 'drive', or RAID-1 2GB, it's what I'd choose, if they do actually do this... ).

      Then get a Lexar CF-card ( up-to 6MB/s, no motor ), up to 1GB 32x [bhphotovideo.com] or 2GB 40x [bhphotovideo.com], or put a MicroDrive on it, and you'll have a VERY mini machine you can FTP to ( probably be able to stick Gentoo on it, if going for a 486-SoC ), if you have to limit everything for power, you may need to limit the amount of RAM on it, when it's in its final config...

      Just ideas, I don't do this stuff day-in-day-out, so I don't know how you'd get it connected to your magnetic-instrument, but I hope this helps..

    • The slowest Seagate 20GB drive i found consumes 24 watts

      Toshiba's 1.8" 20GB drive consumes 1.4W during reading or writing. I imagine the 2.5" drives aren't much worse.

      If it's a power availability problem - spacecraft maybe?... you're not looking for a COTS solution... there would be none. If it's a power DENSITY problem... consolidate all the drive needs in a server away from the environment you're measuring.

      It's not for spacecraft, thankfully. That would open up an entirely new set of problems. This i

    • My entire PowerBook G4, hard drive and all, consumes around that much. You obviously mean full size 3.5" hard drives... Have you considered laptop drives?

  • Do you really need 20Gbyte? (Score:3, Interesting)

    by psyconaut ( 228947 ) on Sunday May 18, 2003 @07:47PM (#5988410)
    I'm interfacing MMCs (could just as well be SD cards in non-secure mode) via SPI to a microcontroller right now for data logging....if ~128-512Mb is sufficient for your application, this is an excellent alternative to rotating storage.

    -psy
    • I'd be interested in how you do this, as I'm currently looking at a similar need for one of my clients and hadn't considered MMC via the SPI interface that we want to use in this project. That could solve the general unavailability problem with large SPI EEPROMs. You can reach me at: dubNO[at-sign]infoSPAMwave.com
  • As others have said, why have you not looked into the 2.5" form-factor laptop hard drives? They're exactly what you want (low power, moderate size, shock resistent) in addition to being a standardized/commodity item. The interface is pretty much the same as any other hard drive (ATAPI), so I don't understand the problem. Or were you just hoping for free product development or something?
    • the problem with laptop HDD's is that since they grab their power from the same power connectors as the data transmit chip does, they can not do long distances like they want. You would need some form of repeater to use a Laptop HDD, and also due to the small ammounts of casing etc... on a laptop HDD, they have a high magnetic interferance (sp?) rating... This also makes them weak to magnetic interferance which might be bad in this situation. As far as data transmition etc goes... an optical transmision

  • USB Laptop HDD (Score:4, Interesting)

    by thecampbeln ( 457432 ) on Sunday May 18, 2003 @07:57PM (#5988447) Homepage
    I picked up a little USB 1.1 Laptop HDD case off of eBay some time back so that I could use an old Laptop drive as an external MP3 repository. As long as the case is plugged into a USB slot that has a full 5v of power it requires no external power supply. Of course since this one is USB 1.1 it's pretty damned slow, but there are USB 2.0 cases like this now a days.

    Of course, you'd need to add USB capabilities to your sensor(s) and you wouldn't really FTP to the drive (I don't believe), but this would be a fairly cheap and modular way to solve your problem.

    But, if you do roll your own HDD that can be dropped into any network with just a Cat5 connection, let us know! ;)

    • Of course, you'd need to add USB capabilities to your sensor(s) and you wouldn't really FTP to the drive (I don't believe), but this would be a fairly cheap and modular way to solve your problem.

      Several people have suggested USB or FW. I have concerns regarding the cable length issue though, which is the primary reason I've been looking for ethernet solutions thus far. I must admit I haven't thoroughly researched how long a USB/FW link can be, but I also chose ethernet for a couple of other reasons I didn'

      • Obviously I don't know your full requirements.

        But, have you thought of using somethink like SMTP (email)? Shoot your data off to some email address (and it could be anywhere). Assuming no data loss (which SMTP/email doesn't guarantee), you'd get a simple approach at data storage.

        Another, possibly more guaranteed and more real-time would be something like Jabber [jabber.org], which is a sort of Instant Messenger transport protocol, where you could define your own packets of data and who/where they'd be sent.

        Though, I

      • I think the Max distance of FW 800 is 100 Meters with fiber cabling. Don't hold me too that though.

  • Flash or power over ethernet (Score:4, Interesting)

    by obtuse ( 79208 ) on Sunday May 18, 2003 @07:58PM (#5988451) Journal
    You might consider using compact flash or a similar medium instead of a HDD. That'll be low power. Otherwise, you might power the device over some of the spare pairs in the ethernet cable. Some telco stuff is implemented that way.

  • Caching strategy (Score:5, Informative)

    by dfranks ( 180507 ) on Sunday May 18, 2003 @07:59PM (#5988460) Homepage
    You didn't say whether you needed 10 watts peak or 10 watts average.

    Assuming it is average and you are doing long term measurements, the average data rate must be pretty low (relative to hard disk transfer rates). So, I would add RAM to the sensor end controller and cache information there until you hit lets say 80% cache full, then fire up the hard disk and do the writes.

    I would use USB 1.1 for the link, controllers are easy to find and cheap, the power requirements are much lower then ethernet+microcontroller+drive interface.

    If your power requirements are peak, then put a lion battery on the hard disk end, charge it from the USB power and operate the drive from that.

    If cost it not a huge issue, you might consider 10 2GB compactflash cards. That would eliminate the need to implement the remote data link.

  • Ethernet uses lots of power... (Score:3, Interesting)

    by Anonymous Coward on Sunday May 18, 2003 @08:32PM (#5988599)
    If you're power sensitive, perhaps ethernet isn't the best technology for you. Ethernet is designed for long distances, and is hardly low power relative to other interconnects. If it's in the budget, maybe you should consider optical fibre channel. Then you would have essentially the power requirements of the disk and the tranciever. Another option would be firewire. It's lower power than ethernet and it has the added benefit of being able to power the drive over the interconnect cable.

  • how sensitive? (Score:4, Insightful)

    by JDizzy ( 85499 ) on Sunday May 18, 2003 @08:43PM (#5988655) Homepage Journal
    Ever heard of Near-End-Atenuation? No? Its the electo-magnetic interferance suffered by telecomm gear when lots a wires draw near each other at the switch. Well, thats the snow-ball effect. No single rain-drop thinks it is the cause of the flood! Anyways, if this sensor gear is so sensitive, then ethernet might be too noisy, electro-magneticly speaking! I would sugest a fiber-optic linkage with a low-powered led that is significantly less noisy, in relative terms comparied to a wire. In an ideal situation the sesor would be away from the data collectors anyways. Oh, and BTW - wireless would in theory trip the sensor too! Seems as if optics is the only real true solution, in my mind anyways. ;)
    • You're thinking of NEXT (near-end crosstalk). Also, 4 wires is not going to cause a NEXT problem; as you mentioned, it only becomes a serious problem when there are a lot of cables in one place. If even ethernet's EMI is too much, shielded cable is an option; just remember to ground it at only one end (or you get nasty ground loops).

      Fiber is nice, but can be hideously expensive; the LED drive circuts might also be a problem if Ethernet is trouble. I would think that a lot of shielding around whatever is

      • Well.. no... I was in fact thinking of "Near-End-Attenuation", as opposed to "Far-End-Attenuation". But its interesting to see other people call it something else, and both terms mean the same thing depending on who you ask, or what books you read. I thought about shielding too, and decided that the whole thing proabbly is shielded to some degree already. I figured that even when shielding, one should still be conservative with noise levels as a matter of principal. I figured why bother with wires when opti
  • Many modern IDE drives have a low-speed setting that reduces the spin rate. It also reduces power consumption and is used in some power-saving modes on some PCs. The only question is, how to get the mini-server to toggle that setting...
  • I'm not sure I understand the issues here. If your sensor gadget has an ethernet port, can't you just run a TP cable to some place where there is power? Or are you looking to have a complete, self-contained system?

    If that's the case, you've made the usual "Ask Slashdot" mistake of phrasing the question in terms of specific and non-essential technology. Instead of an Ethernet port, your device should have an old-fashioned RS-232 port. If your serial hardware meets the spec it will reach 25 feet. (Most RS-2

    • I'm not sure I understand the issues here. If your sensor gadget has an ethernet port, can't you just run a TP cable to some place where there is power? Or are you looking to have a complete, self-contained system?

      Complete, self-contained system that just happens to be in two parts (data collection lump and data storage lump). This system is used for remote, unattended outdoor data collection (remote being the key word). AC power isn't an option at all since even it was available, it creates so much inter

      • ...rather than going into a long diatribe describing every design decision that led us to "ethernet hard drive", I figured it would be best to keep it simple.

        Who was it that said that a system should be as simple as possible, but no simpler? ;)

        I'm not sure RS-232 can make it to 1Mbps, though these guys [bb-elec.com] sell interfaces that go half that fast. Perhaps you could shotgun? You should talk to them in any case -- they seem to know a lot about data collection.

        RS-422 can go up to 2Mbps. I know this because I u

  • What about FibreChannel? (Score:3, Interesting)

    by Amazing Quantum Man ( 458715 ) on Sunday May 18, 2003 @10:18PM (#5989042) Homepage

    If EM interference is an issue, your cabling may cause a problem too... They're a bit pricier, but what about a FibreChannel drive? You've got an optical data path -- no EM interference. Yeah, the adapters cost more, but consider the overall cost for the lab, and the potential EM worries avoided.
  • /. had an article on these recently. I can't find the /. article, but I can find the cited page [baard.com]. It's basically a hard drive and CPU in a tiny little box, with no keyboard or display or anything. This might make it ideal for whatever you want to do: it's smarter and more versatile than a simple hard drive, which gives you a lot more flexibility, and it's designed more specifically for low-power, portable operation.

    I guess it's still in the prototype phase, but you might be able to work with Intel to g

  • Avoid the NAS concept (Score:4, Informative)

    by nathanh ( 1214 ) on Sunday May 18, 2003 @10:45PM (#5989154) Homepage
    I don't need any of the fancy features found in most NAS solutions...I just want a hard drive I can FTP to.

    Sure, but once you specify FTP you then need TCP, which means you need IP, and an FTP server, and a filesystem, and Ethernet, and ... you've just specified a NAS.

    But the problem didn't require a NAS. Your problem was "too much interference so need the hard drive 20 feet away". You could solve this problem with Fibre Channel.

    Investigate an external disk enclosure with fibre channel and a DC power supply. I know Sun was selling these just 2 months ago for desktop external disks.

    • But the problem didn't require a NAS. Your problem was "too much interference so need the hard drive 20 feet away". You could solve this problem with Fibre Channel.

      Several people have suggested Fibre Channel drives. We've discussed the pros and cons of using a fiber link but I kinda lost that battle for a few reasons. However, I didn't have a specific solution in mind when we were discussing it. I'll take a look at the options and see what it would take to implement on the data collection side of things.

  • bus-powered USB drives (Score:4, Informative)

    by g4dget ( 579145 ) on Sunday May 18, 2003 @11:16PM (#5989274)
    There are plenty of bus-powered USB drives for use with laptops. That's the lowest-powered external drive you are likely going to find.

    Don't bother with Ethernet-attached storage; those are not usually designed with low power in mind.
  • buy an old laptop for $300 on ebay and replace its ~4gb hdd with a new 20gb hdd. run your favorite bsd or linux distro on it.

  • mine (Score:3, Interesting)

    by BenTheDewpendent ( 180527 ) <ben@junkns[ ]f.net ['tuf' in gap]> on Monday May 19, 2003 @12:40AM (#5989525) Homepage
    what about the terrapin mine at thinkgeek [thinkgeek.com] its got ethernet and USB. Seems ver flexible. only 10gigs though but you maybe able to drop a 20 or bigger into with minor hacking...
    • Hmm..this thing is interesting. Looks like it might be too "interactive" for unattended use but the idea is close. I'll take a look at it some more and see if I can get some more detailed info.
  • Incredibly sensitive equipment can't be that cheap.

    So why not just use an old laptop?

    get one that will throttle back the prossesor and get all the extra batteries you can.

    should last quite a while, is upgradable to wireless and easy to set an FTP server on.

    It can also have capabilityt added if your needs change.
    • So why not just use an old laptop?

      Good question. This is the most off-the-shelf and flexible solution there is, but it's not the most asthetically pleasing solution. During development this is exactly what we'll use, but eventually this has to be something that's relatively compact and can fit into a weatherproof box. And besides, the laptop consumes a lot more power than we'd like. We can just add more batteries as you suggest, but that gets to be a pain when the batteries get REAL big.

  • take one usb laptop drive. replace cable with laser link.
    problem solved.

    unless you can't provide adequent line-of-sight, that is.

  • iSCSI (Score:2)

    by martin ( 1336 )
    have a look at the latest iSCSI stuff. It may be what you need. Sure you'll have to write a driver but at least you'll have stock parts available.

    Also why can't you put the HD in a faraday cage? Or doesn't that block magnetic fields?
    • have a look at the latest iSCSI stuff. It may be what you need. Sure you'll have to write a driver but at least you'll have stock parts available.

      It's on my list of roll-my-own candidates.

      Also why can't you put the HD in a faraday cage? Or doesn't that block magnetic fields?

      Most Faraday cages are designed to attenuate electric fields only. You can build a magnetic field shield out of high permeability materials such as Mu-metal, but that's a PAIN IN THE ASS. Especially when you want to start passing ri

  • But what about a USB external harddrive?
    Just buy enough USB extensions to put it 20 feet away, and your done. I'm not sure how much power they use, though.
  • OK, this is *completely* off the shelf; no soldering or anything (well, maybe a little for the power arrangement). All you need is a USB HDD and a USB to Ethernet adapter (about $20-$30). Put all this in an environment proof box with some batteries for powering the USB device, link the Ethernet with your monitoring kit and off you go!
    • DOH! You'd need a IP stack at the HDD or another Ethernet to USB at the monitor... my brain's obviously not working after yesterday's late night. Still, instead of implementing Ethernet on the monitoring device using USB/Firewire would probably be a simpler solution.

      Now I've thought it though a bit more, what I'm getting really confused about is this "remote solution to local interference" issue. You can run an Ethernet interface local to the monitor, but not a HDD? What about putting the HDD inside a


  • Would it be possible to add a firewire or usb2 controller to your computer?
    Technically USB1 would even work but it would be slow.

    Get a $80 bridge-board for an IDE harddrive and a 20+ foot cable.

    www.fwdepot.com has bridgeboards, cables, enclosures (if needed) for both firewire and usb.
  • Why does the sensor need to be on the end of an ethernet cable? Couldn't you use something simpler to connect the sensor to the controller board, and keep the controller and the drive close together?

  • iPod (Score:2, Interesting)

    by stang7423 ( 601640 )
    just continuing on with another posters idea of using firewire, why not use an apple iPod. It comes with its own built-in battery and add on batteries are on the way for the new models. Apple states a 10 hour battery life (although it will probably be less if you have to spin the drive all the time).

    As for the distance factor I use a six foot firewire cable with my iPod but I have seen 10 foot cables before, as for 20 foot ??? they might be possible but you might have to build them yourself. I get the
  • Thanks for the replies so far. I left some of the design details out of the original submission to keep the discussion focused, but I guess that's hard to do.

    Most people have suggested USB/FW/FC hard drives instead of ethernet. The 2 problems I can see with this solution are:

    1) The 20 feet distance I mentioned in the original submission is a minimum value. It may have to be further away than that. I'll look into what the real distance limitations of these technologies are. Obviously FibreChannel still sta

    • I'll probably use a single board computer running embedded linux and a 2.5" hard drive.

      You may find the OpenBrick [openbrick.org] to be a good starting point. They take 2.5" drives and run off 5V. Build a DC->DC convertor circuit using something like a MAX787 [maxim-ic.com], or (if you have more heatsinks than time) a 7805, and you should be able to run it off a lead-acid battery a very very long time.

      I have no association with them.

    • just a note of the firewire/ipod angle I posted above. IP over firewire does exist (although it is in most instances beta versions) so attaching a laptop to the other end is also possible for non-dumb storage as you put it.
  • The Linux Kernel supports importing Block Devices over the Network, so it would be really nice to have a harddisk, which can speak NBD over Network. More info about NBD on http://nbd.sf.net/. So if someone is going to develop a Ethernet Harddisk, please consider using NBD as your protocol.
  • Maybe I'm stupid but it seems like you could just enclose a laptop HD in a farraday cage, or some custom made shielding specific to your application. What's harder - developing some hardware control mechanism or using off-the-shelf parts and a thick metal box with a little shielded exit port for an IDE cable? Surely being in the business of desiging high precision sensors you know a thing or two about shield design...
    • What's harder - developing some hardware control mechanism or using off-the-shelf parts and a thick metal box with a little shielded exit port for an IDE cable?

      The latter. :)

      Seriously though, people often underestimate the difficulty in building good low frequency magnetic shields. Electric fields are pretty easy to shield, all you need is a good conductor. For a magnetic shield, you need a material with a high permeability. There are several such materials, but they're far harder to work with. For instan

      • Interesting...what materials (for example) would be employed in shielding magnetic fields from HDs then?

        I never realized it was such a different problem..I guess I should pick up an E&M text sometime..:)

        Note: I really am interested and would like to know some example materials if you have them off the top of your head..
  • For $200 or so you can get a 1GB compact flash card, no magnetic field, no moving parts, size of a matchbook, get rid of that ethernet cable. You can get PCMCIA flash cards up to 4 GB or so but it starts getting pricy after a while.
  • if you urse firewire you could hook a mightly little ipod up to it....20 gigs of storage right there....somewhat low powerconsumption

Slashdot Top Deals

Never ask two questions in a business letter. The reply will discuss the one you are least interested, and say nothing about the other.

Close