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Data Storage Hardware Hacking Build Hardware

Build Your Own SATA Hard Drive Switch 131

Posted by timothy
from the there-can-be-only-one dept.
Mikey Win writes "ExtremeTech shows us a cool hardware hack that allows multiple operating system to boot without dealing with any tedious BIOS setup changes. How? By building your own SATA hard drive switch. The result? You can expect a longer hard drive life span, power supply load reduction, and partitions protected from becoming overwritten or corrupted."
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Build Your Own SATA Hard Drive Switch

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  • I like it (Score:3, Informative)

    by John Napkintosh (140126) on Wednesday February 25, 2009 @04:39PM (#26986443) Homepage

    Low tech and simple. The only thing I might do differently is attach the rotary knob to an unused PCI backplane thingy instead of an unused drive bay - would make it harder for inquisitive people/pets to crash things.

  • Re:I like it (Score:3, Informative)

    by jandrese (485) <kensama@vt.edu> on Wednesday February 25, 2009 @04:50PM (#26986599) Homepage Journal
    The problem with swapping disks constantly is that most drive connectors (don't know about SATA specifically) are really only designed to be swapped a few hundred times at most. The mechanical stress of constantly unplugging and replugging the drive could very well lead to stress fractures in the connector, especially since they're often held on with just solder.
  • Re:I like it (Score:3, Informative)

    by turgid (580780) on Wednesday February 25, 2009 @05:00PM (#26986757) Journal
    After just a couple of dozen swaps, SATA connectors will start to fail. Both the cables and the boards/drives. I know this from bitter experience "enhancing" and testing the very poorly-designed software upgrade mechanism for a storage appliance.
  • Re:I like it (Score:4, Informative)

    by harrkev (623093) <kfmsd@@@harrelsonfamily...org> on Wednesday February 25, 2009 @05:10PM (#26986883) Homepage

    After giving the article a quick skim, it also looks like they switched the ground wires too, which is unnecessary. All you really need to do is to switch the red and yellow wires (+12V a,d +5V). They can all share ground no problem.

  • by Fourier (60719) on Wednesday February 25, 2009 @05:13PM (#26986939) Journal

    Well, if you include a few more pins, then you should be able to merely extend the current design to include the data cables...

    Only if you want to deal with a bunch of CRC failures. You can't really expect to be able to mess around with signal lines when you're switching at 1.5 or 3.0 Gbps.

  • by gweihir (88907) on Wednesday February 25, 2009 @05:37PM (#26987433)

    The design switches ground (Black) as well, instead of keeping it permanently connected. This means that if you use a non-bridging rotary switch (i.e. it does not short out neigbouring connectors when turning it, but has a short phase where all wires are insulated), you could kill disks when switching under power. This happens when +12V and +5V already (or still) have contact but ground does not. The effect is that -7V (a negative voltage) gets applied from Red to Yellow. Typical electronics have a tolerance of -0.5V on their supply lines and die very fast (miliseconds) if that is exceeded in negative direction.

    The same can happen if your (bridging) switch gets a bit corroded and does not make perfect contact anymore. This is not so uncommon.

    My bottom line is that these people have no clue what they are doing and you should under no circumstances copy this faulty design. If at all, then switch only Red and Yellow, but leave Black
    allways connected at all devices. Not only is that safe, there is in fact no sane reason at all to switch Black. I can only conclude that the idea of the designers was to simply switch all wires, without any understanding of the consequences.

    I think this solution is also overdone. I have XP and several Linuxes on a GRUB multi-boot on two computers. True, once or twice per year I need to use a KNOPPIX CD or memory stick to boot my system and reinstall the boot manager. Takes about 5 minutes each time. Not an issue at all.

  • Re:I like it (Score:5, Informative)

    by gweihir (88907) on Wednesday February 25, 2009 @05:44PM (#26987583)

    In fact switching the ground wires under power gives you a high risk of blowing up your drives: If you use a non-bridging switch (or it does not make perfect contact, as cheper ones may do after some time), you can have a situation where +5V and +12V have contact, but ground does not. This typically leads to immediate death of the whole drive electronics.

    These people have no clue what they are doing.

  • Re:I like it (Score:4, Informative)

    by Culture20 (968837) on Wednesday February 25, 2009 @05:46PM (#26987631)
    SATA drive "caddie" manufacturers went cheap when they found out that SATA data and power plug-n-chug easily. Most are just a simple tray to hold-in/lever-out a drive. Even a lot of reasonably old SCSI caddies are this way (but the connectors are much more solid). They're nothing like the IDE/ATA caddies of yore.
  • by gweihir (88907) on Wednesday February 25, 2009 @05:46PM (#26987635)

    Having a signal connected to the hard drive, and no power applied, at least in a traditional TTL or CMOS circuit, is not a good idea.

    Since SATA is based on LVDS, this might not suffer from the typical CMOS or TTL problems, but I would investigate it a bit further.

    SATA has coupling capacitors, so this is not a problem.

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